Semiconductor display device and driving circuit therefor

ABSTRACT

A semiconductor display device with low power consumption, low electromagnetic noise, and low unwanted radiation is provided. In a peripheral driving circuit, a clock signal with a voltage level increased by a level shifter circuit is input to a shift register circuit. Then a timing signal from the shift register circuit is input to a level shifter circuit, and the voltage level is thus raised in two stages.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a semiconductor display device. Morespecifically, it relates to a semiconductor display device whichperforms image display by driving pixel TFTs arranged in a matrix state,and to a semiconductor display device driving circuit. In addition, itrelates to electronic equipment using such semiconductor displaydevices.

2. Description of the Related Art

Recently there has been rapid development in techniques of manufacturingsemiconductor display devices, for example a thin film transistor (TFT),formed from semiconductor thin films on an inexpensive glass substrate.The reason for this is because the demand for active matrix type liquidcrystal display devices has risen.

A TFT is placed in each of the several hundreds of thousands to severalmillions of pixel regions arranged in a matrix state on an active matrixtype liquid crystal display device. The electric charge entering andexiting every pixel electrode is controlled by the switching function ofthe TFT arranged in the pixel regions.

The structure of a conventional active matrix type liquid crystaldisplay device is shown in FIG. 18. A source signal line side drivingcircuit 1801 and a gate signal line side driving circuit 1802 are,normally, generically referred to as driving circuits. In recent yearsthe driving circuit has been formed in unity with the pixel region,which is comprised of the pixel region, on the same substrate.

Further, source signal lines 1803 connected to the source signal lineside driving circuit 1801, and gate signal lines 1804 connected to thegate signal line side driving circuit 1802, intersect in a pixel region1808. Pixel thin film transistors (pixel TFTs) 1805, liquid crystalcells 1806, which sandwich liquid crystals between a pixel electrode andan opposing electrode, and storage capacitors 1807 are formed in theregions surrounded by the source signal lines 1803 and the gate signallines 1804.

An image signal input to the source signal lines 1803 is selected by thepixel TFTs 1805 and written to a predetermined pixel electrode.

Sampling is performed on the image signal in accordance with a timingsignal output from the source signal line side driving circuit 1801, andthe image signal is supplied to the source signal lines 1803.

The pixel TFTs 1805 operate in accordance with a selection signal inputfrom the gate signal line side driving circuit 1802, via the gate signallines 1804.

[Prior Art A]

A block diagram of an example of the conventional source signal lineside driving circuit 1801 is shown in FIG. 19A.

An input signal input from external to the source signal line sidedriving circuit, a clock signal CLK (for example, 3 V), in this case, isinput to the source signal line side driving circuit. The voltageamplitude level of the input clock signal is raised by a level shiftercircuit (for example, from 3 to 16 V).

In the present specification the voltage amplitude level refers to theabsolute value of the difference between the highest electric potentialand the lowest electric potential of a signal. If the voltage amplitudelevel becomes higher (goes up), this means that the electric potentialdifference has become larger, and if the voltage amplitude level becomeslower, this means that the electric potential difference has becomesmaller.

Then the increased voltage amplitude level clock signal is input to theshift register circuit. The shift register circuit operates inaccordance with the input clock signal, and a start pulse signal inputat the same time to the shift register circuit, and creates a timingsignal in order to sample the image signal. The timing signal is inputto a sampling circuit, and the sampling circuit performs sampling of theimage signal based on the input timing signal.

FIG. 21 shows an example of the specific circuit structure of FIG. 19A.A level shifter circuit 11, a shift register circuit 12, a samplingcircuit 13, and an image signal line 14 are arranged as shown in thediagram.

A clock signal CLK and an inverted clock signal CLKb are input to thelevel shifter circuit 11, and a start pulse signal SP and a drivedirection switching signal SL/R are input to the shift register circuit12 from the wirings shown in the drawing.

The clock signal CLK (for example, 3 V) is input to the level shiftercircuit 11 from external to the source signal line side driving circuit.It is necessary for the voltage amplitude level of the clock signal tobe of a voltage amplitude level at which the level shifter circuit 11can operate.

Further, unwanted radiation due to the clock signal is a problem of theset. Unwanted radiation is caused by generation of high frequencycomponents of digital circuits which use rectangular wave trainsstarting up very sharply. Unwanted radiation becomes larger as thesignal frequency gets higher, but it can be suppressed to a certainextent by reducing the voltage amplitude level of the signal.

It is necessary to suppress the unwanted radiation to within the rangeconforming to the standard established by CISPR (the InternationalSpecial Committee on Radio Interference). Furthermore, in addition toCISPR, it is necessary that the range conform to the standardsestablished by other foreign and domestic organizations such as theUnited States FCC (Federal Communications Commission), VCCI (VoluntaryControl Council for Interference by data processing equipment andelectronic office machines), and the German VDE (Verband DeutscherElektrotechniker e.v). For example, the standard established by the FCCIstates that, for industrial equipment, the permitted value of unwantedradiation is 1000 μV when the frequency is from 0.45 to 1.6 MHz, and is3000 μV when the frequency is from 1.6 to 30 MHz. It is necessary toreduce the voltage amplitude level of the clock signal input fromexternal to the source signal line side driving circuit to a level inwhich the unwanted radiation will conform to the standards establishedby the CISPR and other foreign and domestic standards and cause notrouble.

The voltage amplitude level of the clock signal input to the levelshifter circuit increases. An equivalent circuit diagram of the levelshifter circuit 11 is shown in FIG. 20. The reference Vin denotes aninput signal, and Vinb denotes an input of an inverted Vin. In addition,Vddh denotes the application of a positive voltage, and Vss denotes theapplication of a negative voltage. The level shifter circuit 11 isdesigned so that the signal input from Vin, made into a high voltagesignal, and inverted, is then output from Voutb. In short, if Hi isinput to Vin, then a signal corresponding to Vss is output from Voutb,and if Lo is input to Vin, then a signal corresponding to Vddh is outputfrom Vout.

The voltage amplitude level of the clock signal is increased, by a levelshifter like that shown in FIG. 20, to a voltage amplitude level thatincludes a certain fixed margin voltage in addition to a voltageamplitude level at which the liquid crystal is driven to a saturationstate (liquid crystal saturation voltage). Further, saturation voltageindicates the liquid crystal saturation voltage in the presentspecification. A liquid crystal being driven into a saturation stateindicates a state (saturation state) in which a change in theelectro-optical characteristics following change in the liquid crystalarrangement will not accompany a further increase of the appliedvoltage.

The timing signal is a signal used in order to sample the image signalinput to the sampling circuit. The voltage of the timing signal input tothe sampling circuit is then applied to a gate electrode of a TFT whichstructures the analog switch of the sampling circuit. This forms achannel in the TFT which structures the analog switch, and a currentflows from the source to the drain. Thus the image signal is sampled,and this is supplied to the source of the pixel TFT through the sourcesignal line.

For example, for the case of a 5 V drive TN (twisted nematic) liquidcrystal, 5 V is the saturation voltage. An alternating current drivesthe liquid crystal, the result being that −5 V to +5 V, namely a 10 Vvoltage amplitude level, is applied to the liquid crystal. When theliquid crystal is driven in the saturation state, it is necessary tosample a 10 V image signal (in this case the image signal and thesaturation voltage are equal) and supply that to the source of the pixelTFT.

In order to sample this image signal, it is necessary to apply a timingsignal, with a voltage amplitude level that includes a certain fixedmargin voltage (for example, ±3 V) in addition to the saturationvoltage, to the gate of the TF1 that structures the analog switch. Inshort, to sample an image signal voltage of −5 to +5 V, namely a 10 Vvoltage amplitude level image signal, it is necessary that the voltageamplitude level of the timing signal have the absolute value of −8 to 8V, in other words a voltage amplitude level of 16 V.

The margin voltage is a voltage in order to reliably supply a saturationvoltage image signal to the pixel TFT source. There is a problem in thatthe n-channel-type TFT which constitutes the analog switch does notoperate with a ±5 V voltage amplitude level image signal and samplingdoes not occur, when sampling is attempted using a timing signal withthe same ±5 V voltage amplitude level, which does not include a margin.This is because the voltage amplitude level (5 V) of the image signalapplied to the source of the n-channel TFT that constitutes the analogswitch, and the voltage amplitude level (5 V) of the timing signalapplied to the gate electrode, have a voltage amplitude level differenceof 0 V, and the n-channel type TFT does not operate. Further, ap-channel type TFT does not operate for the same reason. Due to this, itis necessary to have the timing signal include a margin voltage in orderto drive the liquid crystal to the saturation state. It is necessarythat the size of the margin voltage be large enough to sample thesaturation voltage image signal in accordance with the timing signal,and to reliably supply the source signal line with the signal.

Additionally, in recent years the development of large screen, highdefinition liquid crystal display devices has been advancing. Whenconsidering display at the same frame rate, the more the number ofpixels in a liquid crystal display device increases, the higher thespeed at which it is necessary to operate the shift register circuit.There is a demand for a higher frequency drive of the shift register.

The operating speed of the shift register circuit is proportional to themobility of the shift register circuit TFT, and to the voltage amplitudelevel of the clock signal applied to the source, and is inverselyproportional to the square of the channel length. The reason that theoperating speed of the shift register circuit is inversely proportionalto the square of the channel length is that if the TFT channel length isshort, the resistance becomes small, and the gate capacitance becomessmall.

In order to operate the shift register circuit at higher speed, it isnecessary to either make the shift register circuit power supply voltagelarge, or to shorten the channel length, because there is a limit to theextent of the TFT mobility.

However, if power supply voltage for the shift register circuit is madehigher, and the channel length is made shorter, the TFT is easilydamaged by punch through and hot electrons caused by the short channeleffect. Therefore it is necessary to lower the shift register circuitpower supply voltage to a level that does not cause damage to the TFT.

In addition, if the voltage amplitude level of the clock signal appliedto the source is reduced to a level that will not damage the TFT due topunch through or hot electrons caused by a short channel effect of theshift register circuit TFT, and if the TFT channel length is madeshorter, then the TFT can not be manufactured due to limits in thedesign of TFTs with short channels. For that reason, the shift resistercircuit can not operate at a speed higher than a certain speed.Therefore, in order to operate the shift register circuit at higherspeed, it is necessary to increase the channel length to a range inwhich it can be made, and to increase the clock signal voltage amplitudelevel applied to the source to a level at which the TFT, with a channellength which can be manufactured, will operate.

In short, in order to operate the shift register circuit at higherspeed, it is necessary to reduce the shift register circuit power supplyvoltage to a level at which the shift register circuit TFT is notdamaged due to punch through or hot electrons by short channel effect,and it is necessary to increase the shift register circuit power supplyvoltage to a level at which the manufacturable channel length TFT willoperate.

In the conventional circuit structure of FIG. 21, the clock signals(CLK, CLKb) input to the shift register circuit TFT become the samevoltage amplitude level as the timing signal input to the samplingcircuit because there is no level shifter circuit in between the shiftregister circuit and the sampling circuit. In other words, the voltageamplitude level of the clock signals input to the shift register circuitcannot be reduced to a level at which damage due to punch through or hotelectrons due to the short channel effect will not occur in the TFT thatconstitutes the shift register circuit. Therefore the shift registercircuit TFT is easily damaged.

There is a solution path for the above problems by using a liquidcrystal display device structured with a LCD material that can be drivenwith a relatively low voltage, smaller than 3 V. However, thereliability is low because the liquid crystal used has a voltage holdingrate that is low, current leaks due to the voltage applied to the liquidcrystals, and the liquid crystals easily deteriorate. LCD materials thatcan be driven with a voltage greater than 3 V have a relatively highvoltage holding rate of over 95%, and the reliability of a liquidcrystal display device that uses an LCD material driven with a voltagegreater than 3 V is high.

[Prior Art B]

A block diagram of another example of the conventional source signalline side driving circuit 1801 is shown in FIG. 19B.

A clock signal CLK (for example, 10 V) input from external to the sourcesignal line side driving circuit is directly input to the shift registercircuit. Then the shift register circuit operates in accordance with theinput clock signal and a start pulse signal input at the same time tothe shift register circuit, and a timing signal is created in order tosample the image.

The created timing signal is input to the level shifter circuit, and thevoltage amplitude level is increased. The timing signal with anincreased voltage amplitude level is input to the sampling circuit, andthe sampling circuit performs sampling of the image signal based on theinput timing signal.

FIG. 22 shows an example of the specific circuit structure of FIG. 19B.A shift register circuit 21, a level shifter circuit 22, a samplingcircuit 23, and an image signal line 24 are arranged as shown in thediagram.

A clock signal CLK, an inverted clock signal CLKb, a start pulse signalSP, and a drive direction switching signal SL/R are input to the shiftregister circuit 21 from the wirings shown in the drawing.

The clock signal CLK (for example, 10 V) is input to the level shiftercircuit 21 from external to the source signal line side driving circuit.The voltage amplitude level of the input clock signal is a voltageamplitude level at which the shift register circuit 21 can operate.

The shift register circuit 21 operates in accordance with the inputclock signal, and the start pulse signal input to the shift registercircuit 21 at the same time, and a timing signal is created in order tosample the image. The created timing signal is input to the levelshifter circuit 22.

It has already been stated that in order to drive the liquid crystal ina saturation state, it is necessary to input a timing signal which has avoltage amplitude level that includes a certain fixed margin voltage inaddition to the saturation voltage, to the sampling circuit 23.Therefore, if the voltage amplitude level of the timing signal input tothe sampling circuit 23 does not meet the voltage amplitude level thatincludes a certain fixed margin voltage in addition to the saturationvoltage, it is necessary to increase the voltage amplitude level of thetiming signal. The timing signal input to the level shifter circuit 22is increased to a voltage amplitude level that includes a certain fixedmargin voltage in addition to the saturation voltage (for example, 16V), and then output. The output timing signal is then input to thesampling circuit 23.

In order to operate the shift register circuit at high-speed, it isnecessary to reduce the power supply voltage of the shift registercircuit to a level that does not cause damage to the TFT of the shiftregister circuit 21 from punch through or hot electrons due to the shortchannel effect. It is also necessary to increase the power supplyvoltage of the shift register circuit to a level at which the TFT, witha manufacturable channel length, will operate. However, with the circuitstructure of Prior Art B, if the voltage amplitude level of the clocksignal, input from external to the source signal line side drivingcircuit, is increased to a high voltage, to a voltage amplitude level atwhich the shift register circuit can operate at high-speed, it isdifficult to suppress the voltage amplitude level of the clock signal,input from external to the source signal line side driving circuit, to alevel at which unwanted radiation does not become a problem. Further,the higher the voltage amplitude level of the clock signal input fromexternal to the source signal line side driving circuit becomes, thelarger the power consumption, which is not desirable.

There is a solution path for the above problems by using a liquidcrystal display device structured with a LCD material that can be drivenwith a relatively low voltage, smaller than 3 V. However, thereliability is low because the liquid crystal used has a voltage holdingrate that is low, current leaks due to the voltage applied to the liquidcrystals, and the liquid crystals easily deteriorate. LCD materials thatcan be driven with a voltage greater than 3 V have a relatively highvoltage holding rate of over 95%, and the o reliability of a liquidcrystal display device that uses an LCD material driven with a voltagegreater than 3 V is high.

[Prior Art C]

A block diagram of another example of the conventional source signalline side driving circuit 1801 is shown in FIG. 19C.

A clock signal CLK (for example, 9 V) from external to the source signalline side driving circuit is input to the shift register circuit. Thenthe shift register circuit operates in accordance with the input clocksignal and a start pulse signal input at the same time to the shiftregister circuit, and a timing signal is created in order to sample theimage. The sampling circuit operates based on the timing signal, and theimage signal is sampled.

FIG. 23 shows an example of the specific circuit structure shown in theblock diagram of FIG. 19C. A shift register circuit 31, a samplingcircuit 32, and an image signal line 33 are arranged as shown in thediagram.

A clock signal CLK, an inverted clock signal CLKb, a start pulse signalSP, and a drive direction switching signal SL/R are input to the shiftregister circuit 31 from the wirings shown in the drawing.

The clock signal CLK (for example, 9 V) is input to the shift registercircuit 31 from external to the source signal line side driving circuit.

The shift register circuit 31 operates in accordance with the inputclock signal, and the start pulse signal input to the shift registercircuit 31 at the same time, and creates in order a timing signal forsampling the image. The created timing signal is input to the samplingcircuit 32.

It is self-evident that the Prior Art C possesses the drawbacks of bothPrior Art A and Prior Art B. If the liquid crystals are driven in thesaturation state, the TFT of the shift register circuit is easilydamaged due to punch through and hot electrons resulting from the shortchannel effect, so there is a problem that the channel length cannot beshortened and therefore high-speed operation is not possible.

Further, with the circuit structure of Prior Art C, at the point ofinput from external to the source signal line side driving circuit, thevoltage amplitude level of the clock signal is a voltage amplitude levelthat includes a certain fixed margin voltage in addition to thesaturation voltage. Therefore this cannot be suppressed enough to avoidthe problems of unwanted radiation and power consumption.

There is a solution path for the above problems by using a liquidcrystal display device structured with a LCD material that can be drivenwith a relatively low voltage, smaller than 3 V. However, thereliability is low because the liquid crystal used has a voltage holdingrate that is low, current leaks due to the voltage applied to the liquidcrystals, and the liquid crystals easily deteriorate. LCD materials thatcan be driven with a voltage greater than 3 V have a relatively highvoltage holding rate of over 95%, and the reliability of a liquidcrystal display device that uses an LCD material driven with a voltagegreater than 3 V is high.

[Prior Art D]

A block diagram a conventional gate signal line side driving circuit isshown in FIG. 24A.

A clock signal CLK (for example, 3 V) from external to the gate signalline side driving circuit is input to the level shifter circuit. Thevoltage amplitude level of the clock signal must be a voltage amplitudelevel at which it is possible for the level shifter circuit to operate.

The voltage amplitude level of the clock signal input to the levelshifter circuit is increased (for example, from 3 V to 25 V).

It is necessary the voltage amplitude level of the selection signalinput to the gate signal lines be a voltage amplitude level at which itis possible to reliably drive all of the pixel TFTs connected to theselected gate signal line. The selected signal voltage is applied to thegate electrodes of the pixel TFTs connected to the gate signal line,forming channels in the pixel TFTs. Thus a current flows from the sourceto the drain of the pixel TFTs, and the image signal is supplied to theliquid crystals, and the liquid crystals are driven.

The gate signal line has a long wiring and the wiring resistance ishigh, so there is a voltage drop when the selection signal input to thegate signal line is applied to the pixel TFT farthest away. The more thevoltage drops, the more the voltage applied to the pixel TFT gateelectrode becomes smaller, and in the worst case a channel cannot beformed in the pixel TFT.

To supply a pixel signal to the liquid crystals by reliably driving allof the pixel TFTs, the voltage amplitude level of the selection signalinput to the gate signal line must be increased to a voltage amplitudelevel that includes a certain fixed margin voltage in addition to theimage signal voltage amplitude level. Also, it is necessary for theselection signal to have a high voltage amplitude level, to a degreewhich the voltage drop due to the wiring resistance of the gate wiringwill not become a problem.

The margin voltage is a voltage in order that an image signal with avoltage amplitude level that is the same as the saturation voltage isreliably supplied to the pixel electrode of the liquid crystal cell. Itis necessary that the margin voltage have a size such that a saturationvoltage image signal will reliably be supplied to the pixel electrode.

The increased voltage amplitude level clock signal (for example, 25 V)is input to the shift register circuit. The shift register circuitoperates in accordance with the input clock signal and a start pulsesignal input to the shift register circuit at the same time, and aselection signal is created in order to operate the pixel TFTs. Thecreated selection signal is input to the gate signal line, channels areformed in the pixel TFTs, and the image signal is supplied to the liquidcrystals.

It is not necessary to operate the shift register circuit at as high aspeed for the gate signal line side driving circuit as it is for thesource signal line side driving circuit. As stated above, the TFToperation speed is inversely proportional to the square of the channellength. The TFT channel length on the shift register circuit is longeron the gate signal line side driving circuit than on the source signalline side driving circuit, which has an operating speed slower than thesource signal line side driving circuit, and it is difficult for damageto occur from punch through or hot electrons due to the short channeleffect.

However, in recent years the development of large screen, highdefinition liquid crystal display devices has been advancing, as statedabove. When considering display at the same frame rate, the more thenumber of pixels in a liquid crystal display device increases, thehigher the speed at which it is necessary to operate the shift registercircuit on the gate signal line side driving circuit, as in the sourcesignal line side driving circuit. Accordingly, there is a demand for ahigher frequency drive of the shift register in the gate signal lineside driving circuit.

Then the increased voltage amplitude level clock signal is input to theshift register circuit. The shift register circuit operates inaccordance with the input clock signal and a start pulse signal input atthe same time to the shift register circuit, and a selection signal iscreated in order to reliably operate the pixel TFTs. The createdselection signal is input to the gate signal lines.

It is self-evident that the Prior Art D possesses the same drawbacks asPrior Art A. With Prior Art D, in order to make it possible to reliablydrive all of the pixel TFTs, it is difficult to reduce the voltageamplitude level of the selection signal input to the shift registercircuit to an extent at which the shift register circuit TFT will not bedamaged from punch through or hot electrons due to the short channeleffect.

There is a solution path for the above problems by using a liquidcrystal display device structured with a LCD material that can be drivenwith a relatively low voltage, smaller than 3 V. However, thereliability is low because the liquid crystal used has a voltage holdingrate that is low, current leaks due to the voltage applied to the liquidcrystals, and the liquid crystals easily deteriorate. LCD materials thatcan be driven with a voltage greater than 3 V have a relatively highvoltage holding rate of over 95%, and the reliability of a liquidcrystal display device that uses an LCD material driven with a voltagegreater than 3 V is high.

[Prior Art E]

A block diagram of another example of a conventional gate signal lineside driving circuit is shown in FIG. 24B.

A clock signal CLK (for example, 10 V) input from external to the gatesignal line side driving circuit is input directly to the shift registercircuit. The input clock signal has a voltage amplitude level at whichit is possible for the shift register circuit to operate. The shiftregister circuit operates in accordance with the input clock signal anda start pulse signal input to the shift register circuit at the sametime, and a selection signal is created in order to operate the pixelTFTs.

The created selection signal is input to the level shifter circuit, andthe voltage amplitude level thereof is increased to a voltage amplitudelevel at which it is possible to reliably operate all of the pixel TFTs(for example, from 10 V to 30 V). The increased voltage amplitude levelselection signal is then supplied to the gate signal lines.

It is self-evident that the Prior Art E possesses the same drawbacks asPrior Art B. With Prior Art B, if the input clock signal is given avoltage amplitude level at which high-speed operation of the shiftregister circuit is possible, then it is difficult to reduce it to adegree at which unwanted radiation will not become a problem. Inaddition, as stated above, there is a problem of not being capable ofsuppressing the power consumption.

There is a solution path for the above problems by using a liquidcrystal display device structured with a LCD material that can be drivenwith a relatively low voltage, smaller than 3 V. However, thereliability is low because the liquid crystal used has a voltage holdingrate that is low, current leaks due to the voltage applied to the liquidcrystals, and the liquid crystals easily deteriorate. LCD materials thatcan be driven with a voltage greater than 3 V have a relatively highvoltage holding rate of over 95%, and the reliability of a liquidcrystal display device that uses an LCD material driven with a voltagegreater than 3 V is high.

[Prior Art F]

A block diagram of another example of a conventional gate signal lineside driving circuit is shown in FIG. 24C.

A clock signal CLK (for example, 20 V) from external to the gate signalline side driving circuit is input to the shift register circuit. Atthis point, the voltage amplitude level of the input clock signal hasthe necessary selection signal voltage amplitude level to drive theliquid crystals in the saturation state.

The shift register circuit then operates in accordance with the clocksignal input to the shift register circuit and a start pulse signalinput to the shift register circuit at the same time, and a selectionsignal is created in order to operate the pixel TFTs. The createdselection signal is input to the gate signal lines.

It is self-evident that the Prior Art F possesses the same drawbacks asPrior Art C. If all of the pixel TFTs are to be reliably driven, thechannel length cannot be shortened because the shift register circuitTFT is easily damaged by punch through and hot electrons due to theshort channel effect, and therefore there is a problem of not beingcable of operating at high-speed.

There is a solution path for the above problems by using a liquidcrystal display device structured with a LCD material that can be drivenwith a relatively low voltage, smaller than 3 V. However, thereliability is low because the liquid crystal used has a voltage holdingrate that is low, current leaks due to the voltage applied to the liquidcrystals, and the liquid crystals easily deteriorate. LCD materials thatcan be driven with a voltage greater than 3 V have a relatively highvoltage holding rate of over 95%, and the reliability of a liquidcrystal display device that uses an LCD material driven with a voltagegreater than 3 V is high.

The problem points from Prior Arts A to F are brought together below. Aliquid crystal display device which can be driven at a relatively lowvoltage below 3V, the voltage holding rate is low, there is a currentleak due to the voltage applied to the liquid crystals, and the liquidcrystals easily deteriorate, so the reliability is low. Thus it isdesirable to increase the liquid crystal display device reliability byusing a display device with a high voltage holding rate and driven witha relatively high voltage. However, if the liquid crystals are driven toa saturation state by a conventional source signal line side drivingcircuit when a liquid crystal display device driven by a relatively highvoltage is used, then the shift register circuit TFT is easily damagedby punch through and hot electrons due to the short channel effect.Further, the change to large scale display panels in recent years hasbrought with it the demand for high-speed operation of the shiftregister circuit. However, if the power consumption and the unwantedradiation with a conventional source signal line side driving circuitare suppressed, high-speed operation of the shift register circuit isdifficult, and the demands accompanying large screens cannot be met.

Similarly for the gate signal line side driving circuit, if all of thepixel TFTs are to be reliably driven, the shift register circuit TFT iseasily damaged by punch through and hot electrons due to the shortchannel effect. If the power consumption and the unwanted radiation aresuppressed, then high-speed operation of the shift register circuit isdifficult, and the demands accompanying large screens cannot be met.

There is a demand for the realization of a driving circuit that candrive without these types of problems, and for a high reliabilitysemiconductor display device which has the driving circuit.

SUMMARY OF THE INVENTION

Thus an object of the present invention is to realize a driving circuitin which a voltage amplitude level of a clock signal input to a shiftregister circuit is set to obtain the voltage and channel lengthsuitable for driving the shift register circuit at high-speed. By doingso, another object of the invention is to realize a high-speed operationdriving circuit, and a semiconductor display device having the drivingcircuit, with which even if liquid crystals are driven in a saturationstate, or even if all of the pixel TFTs are reliably operated, the shiftregister circuit will not be damaged. Further, another object of theinvention is to make high-speed operation of the shift register circuitpossible even if the voltage amplitude level of the clock signal, inputfrom external to the driving circuit, is suppressed to a level at whichpower consumption and unwanted radiation do not become problems.

In the present invention, the voltage amplitude level of the clocksignal input from external to the driving circuit is increased by alevel shifter circuit, and the clock signal is then input to the shiftregister circuit. A timing signal created by the shift register circuitis additionally input to the level shifter circuit. The voltageamplitude level is increased in two stages.

As such, by arranging a level shifter circuit before and after the shiftregister circuit, the present invention reduces the shift registercircuit power supply voltage so that the shift register circuit TFT isnot damaged by punch through or hot electrons due to the short channeleffect. Further, the shift register circuit is operated such that thechannel length of the shift register circuit TFT is lengthened to anextent at which it can be formed, and the voltage amplitude level of theclock signal applied to the TFT source is increased to the level atwhich the TFT operates. Thus, even if the liquid crystals are driven inthe saturation state, and even if all of the pixel TFTs are reliablyoperated, the shift register circuit is not damaged, a driving circuitwhich operates at high-speed, and a semiconductor display device whichcontains the driving circuit are provided. In addition, a semiconductordevice having a driving circuit with which it is possible to suppresspower consumption and unwanted radiation, to such an extent that they donot become problems even when the shift register circuit is operated athigh speed, is provided.

The structure of the present invention is explained below.

In accordance with a preferred embodiment of the present invention,there is provided a source signal line side driving circuit having afirst level shifter circuit, a second level shifter circuit, a shiftregister circuit, and a sampling circuit, characterized in that:

the first level shifter circuit increases the voltage of an inputsignal, which is input to the first level shifter circuit from externalto the source signal line side driving circuit, to a voltage amplitudelevel at which it is possible for the shift register circuit to operate,and inputs the result to the shift resister circuit;

the shift register circuit creates a timing signal, based on the inputsignal input from the first level shifter circuit, in order to sample animage signal supplied from external to the source signal line sidedriving circuit, and inputs the created timing signal to the secondlevel shifter circuit;

the second level shifter circuit further increases the voltage amplitudelevel of the input timing signal, and inputs the result to the samplingcircuit; and

the sampling circuit samples the image signal in accordance with theinput timing signal, and supplies the result to source signal linesconnected to the source signal line side driving circuit. Thus the aboveobjects of the present invention are achieved.

In addition, in accordance with another preferred embodiment of thepresent invention, there is provided a source signal line side drivingcircuit having a first level shifter circuit, a second level shiftercircuit, a shift register circuit, and a sampling circuit, characterizedin that:

the first level shifter circuit increases the voltage of a clock signal,which is input to the first level shifter circuit from external to thesource signal line side driving circuit and has a voltage amplitudelevel at which it is possible for the first level shifter circuit tooperate, to a voltage amplitude level at which it is possible for theshift register circuit to operate, and inputs the result to the shiftregister circuit;

the shift register circuit creates a timing signal, based on the clocksignal input to the shift register circuit, in order to sample an imagesignal supplied from external to the source signal line side drivingcircuit, and inputs the created timing signal to the second levelshifter circuit;

the second level shifter circuit increases the voltage amplitude levelof the timing signal input to the second level shifter circuit, to avoltage amplitude level that includes a certain fixed margin voltage inaddition to the saturation voltage of a liquid crystal, and inputs theresult to the sampling circuit; and

the sampling circuit samples the image signal in accordance with thetiming signal input to the sampling circuit, and supplies the result tosource signal lines connected to the source signal line side drivingcircuit. Thus the above objects of the present invention are achieved.

In addition, in accordance with another preferred embodiment of thepresent invention, there is provided a gate signal line side drivingcircuit having a first level shifter circuit, a second level shiftercircuit, and a shift register circuit, characterized in that:

the first level shifter circuit increases the voltage of an inputsignal, which is input from external to the gate signal line sidedriving circuit, to a voltage amplitude level at which it is possiblefor the shift register circuit to operate, and inputs the result to theshift register circuit;

the shift register circuit creates a selection signal, based on theinput signal which is input to the shift register circuit, and inputsthe created selection signal to the second level shifter circuit; and

the second level shifter circuit increases the voltage amplitude levelof the input selection signal, to a voltage amplitude level at which itis possible for all pixel TFTs connected to gate signal lines toreliably operate, and either directly, or through a buffer circuit,supplies the increased voltage selection signal to the gate signallines. Thus the above objects of the present invention are achieved.

In addition, in accordance with another preferred embodiment of thepresent invention, there is provided a gate signal line side drivingcircuit having a first level shifter circuit, a second level shiftercircuit, and a shift register circuit, characterized in that:

the first level shifter circuit increases the voltage of a clock signal,which is input to the first level shifter circuit from external to thegate signal line side driving circuit and has a voltage amplitude levelat which it is possible for the first level shifter circuit to operate,to a voltage amplitude level at which it is possible for the shiftregister circuit to operate, and inputs the result to the shift registercircuit;

the shift register circuit, based on the clock signal input to the shiftregister circuit, creates a selection signal which operates pixel TFTsconnected to the gate signal line side driving circuit through gatesignal lines, and inputs the created selection signal to the secondlevel shifter circuit; and

the second level shifter circuit increases the voltage amplitude levelof the selection signal input to the second level shifter circuit, to avoltage amplitude level at which it is possible for all of the pixelTFTs connected to the gate signal lines to reliably operate, andsupplies the selection signal, which has been increased in voltage bythe second level shifter circuit, to the gate signal lines. Thus theabove objects of the present invention are achieved.

In addition, in accordance with another preferred embodiment of thepresent invention, there is provided a semiconductor display devicehaving:

a pixel region in which a plurality of pixel TFTs are arranged in amatrix state;

a plurality of source signal lines which are connected to sourceelectrodes of the multiple number of pixel TFTs, respectively;

a plurality of gate signal lines which are connected to gate electrodesof the plurality of pixel TFTs, respectively;

a source signal line side driving circuit connected to the plurality ofsource signal lines; and

a gate signal line side driving circuit connected to the plurality ofgate signal lines, characterized in that:

the source signal line side driving circuit has a first level shiftercircuit, a second level shifter circuit, a shift register circuit, and asampling circuit;

the first level shifter circuit increases the voltage of a clock signal,which is input to the first level shifter circuit from external to thesource signal line side driving circuit and has a voltage amplitudelevel at which it is possible for the first level shifter circuit tooperate, to a voltage amplitude level at which it is possible for theshift register circuit to operate, and inputs the result to the shiftregister circuit;

the shift register circuit creates a timing signal, based on the clocksignal input to the shift register circuit, in order to sample an imagesignal supplied from external to the source signal line side drivingcircuit, and inputs the created timing signal to the second levelshifter circuit;

the second level shifter circuit increases the voltage amplitude levelof the timing signal input to the second level shifter circuit, to avoltage amplitude level that includes a certain fixed margin voltage inaddition to the saturation voltage of a liquid crystal, and inputs theresult to the sampling circuit; and

the sampling circuit samples the image signal in accordance with thetiming signal input to the sampling circuit, and supplies the result tothe source signal lines. Thus the above objects of the present inventionare achieved.

The source signal line side driving circuit may be formed with the pixelregion on the same substrate.

In addition, in accordance with another preferred embodiment of thepresent invention, there is provided a semiconductor display devicehaving:

a pixel region in which a plurality of pixel TFTs are arranged in amatrix state;

a plurality of source signal lines which are connected to sourceelectrodes of the plurality of pixel TFTs, respectively;

a plurality of gate signal lines which are connected to gate electrodesof the plurality of pixel TFTs, respectively;

a source signal line side driving circuit connected to the plurality ofsource signal lines; and

a gate signal line side driving circuit connected to the plurality ofgate signal lines, characterized in that:

the gate signal line side driving circuit has a first level shiftercircuit, a second level shifter circuit, and a shift register circuit;

the first level shifter circuit increases the voltage of a clock signal,which is input to the first level shifter circuit from external to thegate signal line side driving circuit and has a voltage amplitude levelat which it is possible for the first level shifter circuit to operate,to a voltage amplitude level at which it is possible for the shiftregister circuit to operate, and inputs the result to the shift registercircuit;

the shift register circuit, based on the clock signal input to the shiftregister circuit, creates a selection signal which operates the pixelTFTs connected to the gate signal line side driving circuit through thegate signal lines, and inputs the created selection signal to the secondlevel shifter circuit; and

the second level shifter circuit increases the voltage amplitude levelof the selection signal input to the second level shifter circuit, to avoltage amplitude level at which it is possible for all of the pixelTFTs connected to the gate signal lines to reliably operate, andsupplies the selection signal, which has been increased in voltage bythe second level shifter circuit, to the gate signal lines. Thus theabove objects of the present invention are achieved.

The gate signal line side driving circuit may be formed with the pixelregion on the same substrate.

In addition, in accordance with another preferred embodiment of thepresent invention, there is provided a semiconductor display devicehaving:

a pixel region in which a plurality of pixel TFTs are arranged in amatrix state;

a plurality of source signal lines which are connected to sourceelectrodes of the plurality of pixel TFTs, respectively;

a plurality of gate signal lines which are connected to gate electrodesof the plurality of pixel TFTs, respectively

a source signal line side driving circuit connected to the plurality ofsource signal lines; and

a gate signal line side driving circuit connected to the plurality ofgate signal lines, characterized in that:

the source signal line side driving circuit has a first level shiftercircuit, a second level shifter circuit, a first shift register circuit,and a first sampling circuit;

the first level shifter circuit increases the voltage of a clock signal,which is input to the first level shifter circuit from external to thesource signal line side driving circuit and has a voltage amplitudelevel at which it is possible for the first level shifter circuit tooperate, to a voltage amplitude level at which it is possible for thefirst shift register circuit to operate, and inputs the result to thefirst shift register circuit;

the first shift register circuit creates a timing signal, based on theclock signal input to the first shift register circuit, in order tosample an image signal supplied from external to the source signal lineside driving circuit, and inputs the created timing signal to the secondlevel shifter circuit;

the second level shifter circuit increases the voltage amplitude levelof the timing signal input to the second level shifter circuit, to avoltage amplitude level that includes a certain fixed margin voltage inaddition to the saturation voltage of a liquid crystal, and inputs theresult to the first sampling circuit;

the first sampling circuit samples the image signal in accordance withthe timing signal input to the first sampling circuit, and supplies theresult to the source signal lines;

the gate signal line side driving circuit has a third level shiftercircuit, a fourth level shifter circuit, and a second shift registercircuit;

the third level shifter circuit increases the voltage of a clock signal,which is input to the third level shifter circuit from external to thegate signal line side driving circuit and has a voltage amplitude levelat which it is possible for the third level shifter circuit to operate,to a voltage amplitude level at which it is possible for the secondshift register circuit to operate, and inputs the result to the secondshift register circuit;

the second shift register circuit, based on the clock signal input tothe second shift register circuit, creates a selection signal whichoperates the pixel TFTs connected to the gate signal line side drivingcircuit through the gate signal lines, and inputs the created selectionsignal to the fourth level shifter circuit; and

the fourth level shifter circuit increases the voltage amplitude levelof the selection signal input to the fourth level shifter circuit, to avoltage amplitude level at which it is possible for all of the pixelTFTs connected to the gate signal lines to reliably operate, andsupplies the selection signal, which has been increased in voltage bythe fourth level shifter circuit, to the gate signal lines. Thus theabove objects of the present invention are achieved.

The source signal line side driving circuit and the gate signal lineside driving circuit may be formed with the pixel region on the samesubstrate.

In addition, in accordance with another preferred embodiment of thepresent invention, there is provided a driving circuit for asemiconductor display device of digital drive system, the drivingcircuit having a first level shifter circuit, a second level shiftercircuit, a third level shifter circuit, a first latch circuit, a secondlatch circuit, a shift register circuit, and a D/A converter circuit,the driving circuit characterized in that:

the first level shifter circuit increases the voltage of an inputsignal, which is input to the first level shifter circuit from externalto the driving circuit, to a voltage amplitude level at which it ispossible for the shift register circuit to operate, and inputs theresult to the shift register circuit;

the shift register circuit creates a timing signal, based on the inputsignal input from the first level shifter, which determines the timingfor writing a digital signal, supplied from external to the drivingcircuit, to the first latch circuit, and inputs the result to the firstlatch circuit;

the digital signal is input to the third level shifter circuit, and adigital signal output from the third level shifter circuit is input tothe first latch circuit at the timing determined by the timing signal;

the digital signal input to the first latch circuit, after logicaloperation, undergoes logical operation in the second latch circuit, andis output; and

the output digital signal is input to the D/A converter circuit, throughthe second level shifter circuit, and is converted to analog. Thus theabove objects of the present invention are achieved.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIG. 1 is a block diagram of a source signal line side driving circuitof the present invention;

FIG. 2 is a circuit diagram of a source signal line side driving circuitof the present invention;

FIG. 3 is an outline diagram of an active matrix display device;

FIG. 4 is a block diagram of a source signal line side driving circuitof the present invention;

FIG. 5 is a circuit diagram of a source signal line side driving circuitof the present invention;

FIG. 6 is a timing chart of a source signal line side driving circuit ofthe present invention;

FIG. 7 is a block diagram of a source signal line side driving circuitof the present invention;

FIG. 8 is a block diagram of a source signal line side driving circuitof the present invention;

FIG. 9 is a block diagram of a gate signal line side driving circuit ofthe present invention;

FIG. 10 is a circuit diagram of a gate signal line side driving circuitof the present invention;

FIG. 11 is a block diagram of a gate signal line side driving circuit ofthe present invention;

FIGS. 12A to 12E are cross sectional diagrams showing a manufacturingprocess of a TFT;

FIGS. 13A to 13C are cross sectional diagrams showing the manufacturingprocess of TFT;

FIGS. 14A to 14C are cross sectional diagrams showing the manufacturingprocess of a TFT;

FIGS. 15A to 15C are cross sectional diagrams showing the manufacturingprocess of a TFT;

FIGS. 16A to 16E are structural diagrams of electronic equipment usingthe present invention;

FIGS. 17A and 17B are structural diagrams of electronic equipment usingthe present invention;

FIG. 18 is an outline diagram of an active matrix display device;

FIGS. 19A to 19C are block diagrams of conventional source signal lineside driving circuits;

FIG. 20 is an equivalent circuit diagram of a level shifter circuit;

FIG. 21 is a circuit diagram of a conventional source signal line sidedriving circuit;

FIG. 22 is a circuit diagram of a conventional source signal line sidedriving circuit;

FIG. 23 is a circuit diagram of a conventional source signal line sidedriving circuit;

FIGS. 24A to 24C are block diagrams of conventional source signal lineside driving circuits;

FIGS. 25A to 25E are cross sectional diagrams showing a manufacturingprocess of a TFT;

FIGS. 26A to 26D are cross sectional diagrams showing the manufacturingprocess of a TFT;

FIGS. 27A and 27B are cross sectional diagrams showing a manufacturingprocess of a TFT;

FIGS. 28A to 28E are cross sectional diagrams showing a manufacturingprocess of a TFT;

FIGS. 29A and 29B are cross sectional diagrams showing the manufacturingprocess of a TFT;

FIG. 30 is a block diagram of a source signal line side driving circuitof the digital drive system of the present invention;

FIG. 31 is a circuit diagram of a source signal line side drivingcircuit of the digital drive system of the present invention;

FIGS. 32A to 32C are structural diagrams of electronic equipment usingthe present invention;

FIG. 33 is a diagram showing the electro-optical characteristics of amono-stable FLC;

FIGS. 34A to 34B are views showing a structure of an active matrix typeEL display panel;

FIGS. 35A to 35B are views showing a structure of an active matrix typeEL display panel;

FIG. 36 is a view showing a cross section of a pixel region in the anactive matrix type EL display panel;

FIGS. 37A to 37B are views showing a structure of the pixel region in anactive matrix type EL display panel and a circuit structure for thepixel region, respectively;

FIG. 38 is a view showing a structure of a pixel region in an activematrix type EL display panel; and

FIGS. 39A to 39C are views showing circuit structures for pixel regionsin active matrix type EL display panels.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A source signal line side driving circuit is taken as an example of thedriving circuit of the present invention and explained. First, a blockdiagram of the structure of the source signal line side driving circuitis shown in FIG. 1.

A clock signal CLK is input to the source signal line side drivingcircuit from external to the source signal line side driving circuit.

The input clock signal is input to a first level shifter circuit, andthe voltage amplitude level thereof is increased. Then the clock signal,which has a voltage amplitude level increased by the first level shiftercircuit, is input to a shift register circuit. The shift registercircuit operates based on the input clock signal, and in accordance witha start pulse signal input to the shift register circuit at the sametime, and a timing signal for sampling an image is created in order.

The timing signal is input to a second level shifter circuit, and thevoltage amplitude level is increased again. A sampling circuit operatesbased on the timing signal with a voltage amplitude level increased bythe second level shifter circuit, and an image signal is sampled. Thesampled image signal is supplied to source signal lines, and input tothe sources of pixel TFTs.

FIG. 2 shows an example of the circuit structure in the block diagramshown in FIG. 1.

Clock signals CLK and CLKb are input to a first level shifter circuit201 from external to the source signal line side driving circuit. Thevoltage amplitude level of the clock signal needs to be as low aspossible in the range in which the first level shifter circuit 201 canoperate, in order to suppress unwanted radiation to an extent that itdoes not become a problem. It is also necessary in order to limit powerconsumption.

The clock signals input to the first level shifter circuit 201 havetheir voltages increased and then are output. It is necessary toincrease the clock signal voltage amplitude levels at this time to anextent at which a TFT of a shift register circuit 202 is not damaged bypunch through or hot electrons due to the short channel effect, andmoreover to an extent at which a TFT which has a manufacturable channellength will operate.

The clock signals, which have increased voltage amplitude levels due tothe first level shifter circuit 201, are input to the shift registercircuit 202. Further, a start pulse signal SP, with a voltage amplitudelevel increased by a level shifter circuit, is input to the shiftregister circuit 202. The shift register circuit 202 begins operation ofcreating a timing signal, based on the clock signals input to the shiftregister circuit 202, and in accordance with a start pulse signal inputto the shift register circuit at the same time. The timing signaldetermines the sampling timing of an image signal to pixel TFTscorresponding to source signal lines S1 and S2. The timing signalcreated by the shift register circuit 202 is input to a second levelshifter circuit 203.

The voltage of the timing signal input to the second level shiftercircuit 203 is increased. An image signal with a voltage amplitude levelwhich drives the liquid crystals in the saturation state (saturationvoltage) is sampled, so it is necessary to increase the voltage of thetiming signal at this point to a voltage amplitude level that includes acertain fixed margin voltage in addition to the saturation voltage.

The margin voltage is used in order to reliably supply a saturationvoltage image signal to the pixel TFT sources. It is necessary that thesize of the margin voltage be large enough that the saturation voltageimage signal is sampled in accordance with the timing signal, andreliably supplied to the source signal lines S1 and S2.

The timing signal, with its voltage increased by the second levelshifter circuit 203, is input to a sampling circuit 204.

The sampling circuit 204 is an aggregate of analog switches connected toeach of the source lines S1 and S2. When the timing signal is input tothe sampling circuit 204, the timing signal voltage is applied to gateelectrodes of the TFTs that constitute the analog switches of thesampling circuit 204. Thus channels are formed in the TFTs whichcomprise the analog switches, and a current flows from the sources tothe drains. Therefore the image signal is sampled, and supplied to thepixel TFTs through the source signal lines S1 and S2.

In the present invention, by arranging level shifter circuits bothbefore and after the shift register circuit, the shift register circuitTFT is not damaged due to punch through or hot electrons caused by theshort channel effect. Furthermore, by using a clock signal with avoltage amplitude level at which a TFT with a manufacturable channellength operates, the shift register circuit can be operated. As aresult, high-speed operation can be performed without damage to theshift register circuit, and it is possible to drive the liquid crystalsto a saturation state. In addition, even if the voltage amplitude levelof the clock signal input from external to the source signal line sidedriving circuit is reduced as much as possible within the range in whichthe level shifter circuit can operate, high-speed operation of the shiftregister circuit is possible, so power consumption and unwantedradiation can be suppressed to such an extent that they do not becomeproblems.

A driving circuit of the present invention, and a semiconductor devicewhich has the driving circuit, are explained in detail using FIGS. 3 to17B by embodiments below.

[Embodiment 1]

An example of a source signal line side driving circuit using thestructure of the present invention, in which, by arranging level shiftercircuits before and after a shift register circuit, the voltageamplitude level of a signal is increased in two stages, before and afterthe shift register circuit, is shown in Embodiment 1. The structure of asemiconductor device of Embodiment 1, in particular an active matrixtype liquid crystal display device, is shown in FIG. 3.

A source signal line side driving circuit 301 and a gate signal lineside driving circuit 302 are formed in unity on the same substrate as apixel region which constitutes a pixel region 308.

In addition, a plurality of source signal lines 303 connected to thesource signal line side driving circuit 301, and a plurality of gatesignal lines 304, connected to the gate signal line side driving circuit302, intersect in the pixel region 308. Formed in the region enclosed byeach of the source signal lines 303 and each of the gate signal lines304 are a liquid crystal cell 306, in which a liquid crystal issandwiched by a pixel electrode and an opposing electrode, a storagecapacitor 307, and one out of a plurality of pixel TFTs 305 connected tothe source signal lines 303 and the gate signal lines 304.

An image signal input to the source signal lines 303 is selected by thepixel TFTs 305, and written to preset pixel electrodes.

The image signal, sampled in accordance with a timing signal output fromthe source signal line side driving circuit 301, is supplied to thesource signal lines 303 by a sampling circuit.

The pixel TFTs 305 operate in accordance with the selection signaloutput from the gate signal line side driving circuit 302 through thegate signal lines 304.

Next, a block diagram of the source signal line side driving circuit ofEmbodiment 1 is shown in FIG. 4. A liquid crystal with a saturationvoltage of 5 V is used in Embodiment 1. A clock signal CLK, with avoltage amplitude level of 2.5 V and from external to the source signalline side driving circuit, is input to a first level shifter circuit ofthe source signal line side driving circuit. The voltage amplitude levelof the clock signal input to the first level shifter circuit needs to beas low as possible, within the range in which the first level shiftercircuit can operate, in order to suppress unwanted radiation to anextent where it does not become a problem. This is also necessary inorder to reduce power consumption.

The voltage amplitude level of the clock signal input to the first levelshifter circuit is increased (made higher voltage) by the first levelshifter circuit, from 2.5 V to 5 V in Embodiment 1, and the result isinput to the shift register circuit.

The voltage amplitude level of the clock signal input to the shiftregister circuit is required to be a voltage amplitude level that iswithin the range in which the shift register circuit can operate. Theshift register circuit can operate at 5 V in Embodiment 1. For example,in order to operate the shift register circuit of the source signal lineside driving circuit at 12.5 MHz or greater in Embodiment 1, whenconfigured by a TFT with a 2 μm channel length, it is necessary for thevoltage amplitude level of the clock signal input to the shift registercircuit to be 4 V or greater. The voltage amplitude level is increasedto 5 V in Embodiment 1, but the voltage amplitude level is not limitedto this number for the present invention. A necessary condition is thatthe voltage amplitude level of the clock signal input to the shiftregister circuit be within the range in which the shift register circuitcan operate. Further, the level shifter circuit may be used for signalsother than just the clock signal, such as a start pulse signal.

The 5 V voltage amplitude level clock signal output from the levelshifter circuit is input to the shift register circuit. The shiftregister circuit operates based on the clock signal input to the shiftregister circuit, and in accordance with the start pulse signal input tothe shift register circuit at the same time, and creates a timing signalin order to sample the image signal supplied from an image signal line.The created timing signal is input to a second level shifter circuit.

The voltage amplitude level of the timing signal input to the secondlevel shifter circuit is increased by the second level shifter circuit.It is necessary for the timing signal to be increased to a voltageamplitude level that includes a certain fixed margin voltage in additionto the saturation voltage. The timing signal input to the second levelshifter circuit at 5 V is increased to 12 V, and the 12 V timing signalis input to the sampling circuit. The sampling circuit performs asampling operation on the image signal supplied from the image signallines in accordance with the timing signal input to the samplingcircuit.

The sampled image signal is supplied to the source signal lines, and isinput to the pixel TFTs connected to the source signal lines, operatingthe liquid crystals.

Note that a specific circuit diagram of the source signal line sidedriving circuit of Embodiment 1 is shown in FIG. 5, and timing chart ofthe specific circuit of this embodiment shown in FIG. 5, at the clocksignal, points A, B1, B2, C1, C2, and on the timing signal lines S1 andS2 is shown in FIG. 6.

The 2.5 V voltage amplitude level clock signal CLK is amplified to 5 Vby a first level shifter circuit 501 (point A). The increased voltageamplitude level clock signal is input to a shift register circuit 502, astart pulse signal SP, with its voltage amplitude level increased by alevel shifter circuit, is input to the shift register circuit 502 at thesame time, and a timing signal is created (points B1 and B2).

The timing signal is further amplified by a second level shifter circuit503, becoming 12 V (points C1 and C2). Then the timing signal is inputto an analogue switch 505, the image signal is sampled, and the imagesignal is supplied to the selected source signal lines S1 and S2.

Thus, by arranging level shifter circuits both before and after theshift register circuit with the present invention, a clock signal with avoltage amplitude level low enough to cause no damage to the shiftregister circuit TFT from punch through or hot electrons due to theshort channel effect, and high enough that a TFT with a manufacturablechannel length will operate, can be input to the shift register circuit.As a result, the shift register circuit can be operated at higher speed.Further, even if the voltage amplitude level of the clock signal inputfrom external to the source signal line side driving circuit is reducedas much as possible within the range in which the level shifter circuitcan operate, high-speed operation of the shift register circuit ispossible, so power consumption and unwanted radiation can be suppressedto an extent that they do not become problems. An example of the presentinvention applied to a source signal line side driving circuit isexplained in Embodiment 1, but the present invention is not limited tothe preferred embodiment of Embodiment 1.

[Embodiment 2]

Another example of a source signal line side driving circuit using thestructure of the present invention, in which, by arranging level shiftercircuits before and after a shift register circuit, the voltageamplitude level of a signal is increased in two stages, before and afterthe shift register circuit, is shown in Embodiment 2.

Next, a block diagram of the source signal line side driving circuit ofEmbodiment 2 is shown in FIG. 7. In Embodiment 2 a liquid crystal with asaturation voltage of 6 V is used. A clock signal CLK, with a voltageamplitude level of 3 V and from external to the source signal line sidedriving circuit, is input to a first level shifter circuit of the sourcesignal line side driving circuit. The voltage amplitude level of theclock signal input to the first level shifter circuit needs to be as lowas possible, within the range in which the first level shifter circuitcan operate, in order to suppress unwanted radiation to an extent whereit does not become a problem. This is also necessary in order to reducepower consumption.

The voltage amplitude level of the clock signal input to the first levelshifter circuit is increased (made higher voltage) by the first levelshifter circuit, from 3 V to 10 V in Embodiment 2, and the result isinput to the shift register circuit.

The voltage amplitude level of the clock signal input to the shiftregister circuit is required to be a voltage amplitude level that iswithin the range in which the shift register circuit can operate. Theshift register circuit can operate at 10 V in Embodiment 2. For example,in order to operate the shift register circuit of the source signal lineside driving circuit at 5 MHz or greater in Embodiment 2, whenconfigured by a TFT with a 3 μm channel length, it is necessary for thevoltage amplitude level of the clock signal input to the shift registercircuit to be 8 V or greater. The voltage amplitude level is increasedto 10 V in Embodiment 2, but the voltage amplitude level is not limitedto this number for the present invention. A necessary condition is thatthe voltage amplitude level of the clock signal input to the shiftregister circuit be within the range in which the shift register circuitcan operate. Further, the level shifter circuit may be used for signalsother than just the clock signal, such as a start pulse signal.

The 10 V voltage amplitude level clock signal output from the levelshifter circuit is input to the shift register circuit. The shiftregister circuit operates based on the clock signal input to the shiftregister circuit, and in accordance with the start pulse signal input tothe shift register circuit at the same time, and creates a timing signalin order to sample an image signal supplied from an image signal line.The created timing signal is input to a second level shifter circuit.

The voltage amplitude level of the timing signal input to the secondlevel shifter circuit is increased by the second level shifter circuit.It is necessary for the timing signal to be increased to a voltageamplitude level that includes a certain fixed margin voltage in additionto the saturation voltage. The timing signal input to the second levelshifter circuit at 10 V is increased to 15 V, and the 15 V timing signalis input to the sampling circuit. The sampling circuit performs asampling operation on the image signal supplied from the image signallines in accordance with the timing signal input to the samplingcircuit.

The sampled image signal is supplied to the source signal lines, and isinput to the pixel TFTs connected to the source signal lines, operatingthe liquid crystals.

Thus, by forming level shifter circuits both before and after the shiftregister circuit with the present invention, a clock signal with avoltage amplitude level low enough to cause no damage to the shiftregister circuit TFT from punch through or hot electrons due to theshort channel effect, and high enough that a TFT with a manufacturablechannel length will operate, can be input to the shift register circuit.As a result, the shift register circuit can be operated at higher speed.Further, even if the voltage amplitude level of the clock signal inputfrom external to the source signal line side driving circuit is reducedas much as possible within the range in which the level shifter circuitcan operate, high-speed operation of the shift register circuit ispossible, so power consumption and unwanted radiation can be suppressedto an extent that they do not become problems. An example of the presentinvention applied to a source signal line side driving circuit isexplained in Embodiment 2, but the present invention is not limited tothe preferred embodiment of Embodiment 2.

[Embodiment 3]

Another example of a source signal line side driving circuit using thestructure of the present invention, in which, by arranging level shiftercircuits before and after a shift register circuit, the voltageamplitude level of a signal is increased in two stages, before and afterthe shift register circuit, is shown in Embodiment 3.

Next, a block diagram of the source signal line side driving circuit ofEmbodiment 3 is shown in FIG. 8. In Embodiment 3 a liquid crystal with asaturation voltage of 7 V is used. A clock signal CLK, with a voltageamplitude level of 5 V and from external to the source signal line sidedriving circuit, is input to a first level shifter circuit of the sourcesignal line side driving circuit. The voltage amplitude level of theclock signal input to the first level shifter circuit needs to be as lowas possible, within the range in which the first level shifter circuitcan operate, in order to suppress unwanted radiation to an extent whereit does not become a problem. This is also necessary in order to reducepower consumption.

The voltage amplitude level of the clock signal input to the first levelshifter circuit is increased (made higher voltage) by the first levelshifter circuit, from 5 V to 12 V in Embodiment 3, and the result isinput to the shift register circuit.

The voltage amplitude level of the clock signal input to the shiftregister circuit is required to be a voltage amplitude level that iswithin the range in which the shift register circuit can operate. Theshift register circuit can operate at 12 V in Embodiment 3. For example,in order to operate the shift register circuit of the source signal lineside driving circuit at 3 MHz or greater in Embodiment 3, whenconfigured by a TFT with a 5 μm channel length, it is necessary for thevoltage amplitude level of the clock signal input to the shift registercircuit to be 10 V or greater. The voltage amplitude level is increasedto 12 V in Embodiment 3, but the voltage amplitude level is not limitedto this number for the present invention. A necessary condition is thatthe voltage amplitude level of the clock signal input to the shiftregister circuit be within the range in which the shift register circuitcan operate. Further, the level shifter circuit may be used for signalsother than just the clock signal, such as a start pulse signal.

The 12 V voltage amplitude level clock signal output from the levelshifter circuit is input to the shift register circuit. The shiftregister circuit operates based on the clock signal input to the shiftregister circuit, and in accordance with the start pulse signal input tothe shift register circuit at the same time, and creates a timing signalin order to sample an image signal supplied from an image signal line.The created timing signal is input to a second level shifter circuit.

The voltage amplitude level of the timing signal input to the secondlevel shifter circuit is increased by the second level shifter circuit.It is necessary for the timing signal to be increased to a voltageamplitude level that includes a certain fixed margin voltage in additionto the saturation voltage. The timing signal input to the second levelshifter circuit at 12 V is increased to 18 V, and the 18 V timing signalis input to the sampling circuit. The sampling circuit performs asampling operation on the image signal supplied from the image signallines in accordance with the timing signal input to the samplingcircuit.

The sampled image signal is supplied to the source signal lines, and isinput to the pixel TFTs connected to the source signal lines, operatingthe liquid crystals.

Thus, by arranging level shifter circuits both before and after theshift register circuit with the present invention, a clock signal with avoltage amplitude level low enough to cause no damage to the shiftregister circuit TFT from punch through or hot electrons due to theshort channel effect, and high enough that a TFT with a manufacturablechannel length will operate, can be input to the shift register circuit.As a result, the shift register circuit can be operated at higher speed.Further, even if the voltage amplitude level of the clock signal inputfrom external to the source signal line side driving circuit is reducedas much as possible within the range in which the level shifter circuitcan operate, high-speed operation of the shift register circuit ispossible, so power consumption and unwanted radiation can be suppressedto an extent that they do not become problems. An example of the presentinvention applied to a source signal line side driving circuit isexplained in Embodiment 3, but the present invention is not limited tothe preferred embodiment of Embodiment 3.

[Embodiment 4]

An example of the structure of the present invention applied to a gatesignal line side driving circuit is explained in Embodiment 4.

A block diagram of the gate signal line side driving circuit ofEmbodiment 4 is shown in FIG. 9. In Embodiment 4 a liquid crystal with asaturation voltage of 15 V is used. A clock signal CLK, with a voltageamplitude level of 3 V and from external to the gate signal line sidedriving circuit, is input to a first level shifter circuit of the gatesignal line side driving circuit. The voltage amplitude level of theclock signal input to the first level shifter circuit needs to be as lowas possible, within the range in which the first level shifter circuitcan operate, in order to suppress unwanted radiation to an extent whereit does not become a problem. This is also necessary in order to reducepower consumption.

The voltage amplitude level of the clock signal input to the first levelshifter circuit is increased (made higher voltage) by the first levelshifter circuit, from 3 V to 10 V, and the result is input to the shiftregister circuit.

The voltage amplitude level of the clock signal input to the shiftregister circuit is required to be a voltage amplitude level that iswithin the range in which the shift register circuit can operate. Thevoltage amplitude level is increased to 10 V in Embodiment 4, but thevoltage amplitude level is not limited to this number for the presentinvention. A necessary condition is that the voltage amplitude level ofthe clock signal input to the shift register circuit be within the rangein which the shift register circuit can operate. Further, the levelshifter circuit may be used for signals other than just the clocksignal, such as a start pulse signal.

The 10 V voltage amplitude level clock signal output from the levelshifter circuit is input to the shift register circuit. The shiftregister circuit operates based on the clock signal input to the shiftregister circuit, and in accordance with the start pulse signal input tothe shift register circuit at the same time, and creates a selectionsignal in order to reliably operate all pixel TFTs connected to gatesignal lines. The created selection signal is input to a second levelshifter circuit.

The voltage amplitude level of the selection signal input to the secondlevel shifter circuit is increased by the second level shifter circuit.It is necessary for the selection signal to be increased to a voltageamplitude level required to reliably operate all the pixel TFTs. Theselection signal input to the second level shifter circuit at 10 V isincreased to 20 V, the 20 V selection signal is input to the gate signallines, and the pixel TFTs operate to supply an image signal to liquidcrystals.

A specific circuit structure of the block diagram of FIG. 9 is shown inFIG. 10.

The clock signal CLK, input to a first level shifter circuit 1001, isincreased in voltage and then output. At this point the voltageamplitude level of the clock signal has a voltage amplitude level atwhich the level shifter circuit 1001 can operate, and it is desirablethat the voltage amplitude level is lower than the selection signalvoltage amplitude level required to reliably operate all of the pixelTFTs. The clock signal is input to a shift register circuit 1002.

A start pulse signal SP with a voltage amplitude level increased by alevel shifter circuit is input to the shift register circuit 1002. Theshift register circuit 1002 begins to operate at a preset timing inaccordance with the input of the start pulse signal. Then, based on theclock signal input to the shift register circuit 1002, a selectionsignal which drives the pixel TFTs is output in order, and then input toa second level shifter circuit 1003.

The selection signal input to the second level shifter circuit 1003 isincreased in voltage again and then output. The selection signal with anincreased voltage is then input to the gate signal lines g1, g2, and g3.At this point it is necessary that the voltage amplitude level beincreased to the selection signal voltage amplitude level required toreliably operate all of the pixel TFTs.

Thus, by arranging level shifter circuits both before and after theshift register circuit, a clock signal with a voltage amplitude levellow enough to cause no damage to the shift register circuit TFT frompunch through or hot electrons due to the short channel effect, and yethigh enough that a TFT with a manufacturable channel length willoperate, can be input to the shift register circuit. And powerconsumption can be suppressed. Further, even if the voltage amplitudelevel of the clock signal input from external to the gate signal lineside driving circuit is reduced as much as possible within the range inwhich the level shifter circuit can operate, high-speed operation of theshift register circuit is possible, so power consumption and unwantedradiation can be suppressed to an extent that they do not becomeproblems. An example of the present invention applied to a gate signalline side driving circuit is explained in Embodiment 4, but the presentinvention is not limited to the preferred embodiment of Embodiment 4.

Note that it is possible to use the gate signal line side drivingcircuit shown in Embodiment 4 in the active matrix type liquid crystaldisplay device shown in FIG. 3 of Embodiment 1.

[Embodiment 5]

Another example of the structure of the present invention applied to agate signal line side driving circuit is explained in Embodiment 5.

A block diagram of the gate signal line side driving circuit ofEmbodiment 5 is shown in FIG. 11. In Embodiment 5 a liquid crystal witha saturation voltage of 14 V is used. A clock signal CLK, with a voltageamplitude level of 5 V and from external to the gate signal line sidedriving circuit, is input to a first level shifter circuit of the gatesignal line side driving circuit. The voltage amplitude level of theclock signal input to the first level shifter circuit needs to be as lowas possible, within the range in which the first level shifter circuitcan operate, in order to suppress unwanted radiation to an extent whereit does not become a problem. This is also necessary in order to reducepower consumption.

The voltage amplitude level of the clock signal input to the first levelshifter circuit is increased (made higher voltage) by the first levelshifter circuit, from 5 V to 12 V, and the result is input to the shiftregister circuit.

The voltage amplitude level of the clock signal input to the shiftregister circuit is required to be a voltage amplitude level that iswithin the range in which the shift register circuit can operate. Thevoltage amplitude level is increased to 12 V in Embodiment 5, but thevoltage amplitude level is not limited to this number for the presentinvention. A necessary condition is that the voltage amplitude level ofthe clock signal input to the shift register circuit be within the rangein which the shift register circuit can operate. Further, the levelshifter circuit may be used for signals other than just the clocksignal, such as a start pulse signal.

The 12 V voltage amplitude level clock signal output from the firstlevel shifter circuit is input to the shift register circuit. The shiftregister circuit operates based on the clock signal input to the shiftregister circuit, and in accordance with the start pulse signal input tothe shift register circuit at the same time, and creates a selectionsignal in order to reliably operate all pixel TFTs connected to gatesignal lines. The created selection signal is input to a second levelshifter circuit.

The voltage amplitude level of the selection signal input to the secondlevel shifter circuit is increased by the second level shifter circuit.It is necessary for the selection signal to be increased to a voltageamplitude level required to reliably operate all the pixel TFT's. Theselection signal input to the second level shifter circuit at 12 V isincreased to 25 V, the 25 V selection signal is input to the gate signallines, and the pixel TFTs operate to supply an image signal to liquidcrystals. The image is therefore displayed in the liquid crystaldisplay.

Thus, by arranging level shifter circuits both before and after theshift register circuit with the present invention, a clock signal with avoltage amplitude level low enough to cause no damage to the shiftregister circuit TFT from punch through or hot electrons due to theshort channel effect, and yet high enough that a TFT with amanufacturable channel length will operate, can be input to the shiftregister circuit. As a result, the shift register circuit can beoperated at higher speed, and power consumption can be suppressed.Further, even if the voltage amplitude level of the clock signal inputfrom external to the gate signal line side driving circuit is reduced asmuch as possible within the range in which the level shifter circuit canoperate, high-speed operation of the shift register circuit is possible,so power consumption and unwanted radiation can be suppressed to anextent that they do not become problems. An example of the presentinvention applied to a gate signal line side driving circuit isexplained in Embodiment 5, but the present invention is not limited tothe preferred embodiment of Embodiment 5.

[Embodiment 6]

The present invention may be applied to both a source signal line sidedriving circuit and a gate signal line side driving circuit. In thiscase, the source signal line side driving circuit and the gate signalline side driving circuit each use a first and a second level shiftercircuit. For example, a combination of the above embodiments may bemade.

[Embodiment 7]

A manufacturing process of the active matrix type liquid crystal displaydevice of the above Embodiments 1 to 6 is explained in Embodiment 7.

This embodiment describes with reference to FIGS. 12A to 15C an examplein which a plurality of top gate type TFTs are formed on a substratehaving an insulating surface, and in which a pixel region circuit and anoperation circuit that includes a level shifter circuit and a shiftregister circuit are monolithically formed. Note that a CMOS circuitthat is a basic circuit is shown as an example of a driving circuit suchas a logic circuit, in Embodiment 7. Note also that, although themanufacturing process of a CMOS circuit configured with a p-channel typeTFT and an n-channel type TFT each having one gate electrode isexplained in Embodiment 7, a multiple gate electrode CMOS circuit suchas a double gate CMOS circuit can also be manufactured in the same way.

Please refer to FIG. 12A. First, a glass substrate 601 is prepared as asubstrate having an insulating surface. A quartz substrate or athermally oxidized film silicon substrate may be substituted for theglass substrate. In addition, a method may be used by which an amorphoussilicon film is formed on a quartz substrate, and is then completelyoxidized by heat into an insulating film. Further, a quartz substrate, aceramic substrate, or a silicon substrate, each with a silicon nitridefilm as the insulating film, may be used. In Embodiment 7 a base filmcomprising silicon oxide 602 is formed on the glass substrate 601 tohave a thickness of 200 nm. The base film may be a laminated film ofsilicon nitride films, or a silicon nitride film only.

Reference numeral 603 denotes an amorphous silicon film, and adjustmentis made so that its final film thickness (the film thickness determinedby considering film reduction after thermal oxidation) is from 10 to 75nm (desirable from 15 to 45 nm). Note that it is important to thoroughlycontrol the concentration of impurities throughout the film whendepositing the film.

The concentrations of all typical impurities such as C (carbon), N(nitrogen), O (oxygen), and S (sulphur) are controlled to be less than5×10¹⁸ atoms/cm³ (desirable 1×10¹⁸ atoms/cm³ or less) throughout theamorphous silicon film 603 in the case of Embodiment 7. If any of theimpurities exists at a higher concentration, this will have a badinfluence during crystallization, and will become a cause of reducedfilm quality after crystallization.

Note that the concentration of hydrogen throughout the amorphous siliconfilm 603 is also a very important parameter, and that by reducing thehydrogen content, a film with better crystallinity can be obtained.Therefore it is desirable to use low pressure thermal CVD to deposit theamorphous silicon film 603. Note that by optimizing the film depositionconditions, it is also possible to use plasma CVD.

Next, a crystallization process is performed on the amorphous siliconfilm 603. The technique of Japanese Patent Application Laid-open No. Hei7-130652 may be used as the crystallization means. The means in eitherEmbodiment 1 or Embodiment 2 of the above patent application may beused, and it is desirable that the technique contents described inEmbodiment 2 of the above patent application (details in Japanese PatentApplication Laid-open No. Hei 8-78329) be used here for Embodiment 7.

First a mask insulating film 604, which selects catalytic element dopingregions, is formed according to the technique of Japanese PatentApplication Laid-open No. Hei 8-78329. The mask insulating film 604 hasopenings in several locations in order to dope the catalytic element.The location of the crystalline regions can be determined by thelocations of the openings.

A solution containing nickel (Ni) as the catalytic element to promotecrystallization of the amorphous silicon film 603 is then applied byspin coating, forming a Ni containing layer 605. Note that other thannickel, cobalt (Co), iron (Fe), palladium (Pd), platinum (Pt), copper(Cu), and gold (Au), etc., can be used as the catalytic element. (SeeFIG. 12B.)

In addition, ion implantation and plasma doping employing a resist maskcan be used for the above catalytic element doping process. In this caseit is easy to reduce the area occupied by the doping region, and tocontrol growth distance in a lateral growth region, so this is aneffective technique when constructing a scaled down circuit.

Next, after dehydrogenation at 450° C. for one hour after the catalyticelement doping process is completed, a 4 to 24 hour heat treatment atbetween 500 and 700° C. (typically from 550 to 650° C.) in an inert,hydrogen or oxygen atmosphere is carried out to crystallize theamorphous silicon film 603. The heat treatment is performed at 570° C.for 14 hours in a nitrogen atmosphere in Embodiment 7.

At this point the crystallization of the amorphous silicon film 603advances preferentially from nickel doped regions 606, or from seedsgenerated in the nickel doped regions 606, forming crystalline regions607 which have grown almost parallel to the substrate surface of theglass substrate 601. The crystalline regions 607 are called lateralgrowth regions. Individual crystals are gathered in a relatively alignedstate in the lateral growth regions, so there is an advantage in thatthe overall crystallinity is superior. (See FIG. 12C.)

Note that regions that can microscopically be called lateral growthregions are formed by use of the technique described in Embodiment 1 ofthe above stated Japanese Patent Application Laid-open No. Hei 7-130652.However, seed generation occurs non-uniformly inside the surface, so thetechnique can be criticized from the point of controllability of thegrain boundaries.

Phosphorous is next doped in this state in order to remove the nickelthroughout the film. Phosphorous is only doped into the nickel dopedregion 606 by doing so. These regions are denoted as phosphorous dopedregions 608. At this point the doping acceleration voltage and thethickness of the mask insulating film 604 made of an oxidized film areoptimized so that phosphorous does not substantially penetrate the maskinsulating film 604. (See FIG. 12D.)

A phosphorous dose in a range from 1×10¹⁴ to 1×10¹⁵ ions/cm² isdesirable. In Embodiment 7 a dose of 5×10¹⁴ ions/cm² is doped using anion doping apparatus.

Note that the acceleration voltage is 10 kV when ion doping. Almost nophosphorous can pass through a 1000 Å insulating film mask if theacceleration voltage is 10 kV.

FIG. 12E is referred to next. Thermal annealing in a nitrogen atmosphereat 600° C. for between 1 and 12 hours (for 12 hours in Embodiment 7) isthen performed, gettering the nickel element. Annealing causes thenickel to be drawn to the phosphorous. At a temperature of 600° C.,phosphorous atoms have almost no motion in the film, but nickel atomscan move a distance of several hundred micrometers or more. Thus it canbe understood that phosphorous is one of the most suitable elements forthe gettering of nickel.

The mask insulating film 604 is removed and patterning is performedafter completion of a heat treatment for crystallization, forming islandshaped semiconductor layers (active layers) 609, 610, and 611 from thelateral growth regions 607. (See FIG. 13A.)

Reference numeral 609 denotes an active layer of an n-type TFT whichconstitutes the CMOS circuit, 610 denotes an active layer of a p-typeTFT which constitutes the CMOS circuit, and 611 denotes an active layerof an n-type TFT (pixel TFT) that constitutes the pixel region.

After forming the active layers 609, 610, and 611, a gate insulatingfilm 612 made from an insulating film containing silicon is deposited ontop.

Next, a metallic film, containing aluminum as its major constituentelement and not shown in the figures, is deposited, forming the baseshape of a later gate electrodes by patterning. An aluminum filmcontaining 2 wt % scandium is used in Embodiment 7.

Next, porous anodic oxidation films 613 to 620, non-porous anodicoxidation films 621 to 624, and gate electrodes 625 to 628 are formed inaccordance with the technique of Japanese Patent Application Laid-openNo. Hei 7-135318. (See FIG. 13B.)

After obtaining the state in FIG. 13B, the gate electrodes 625 to 628and the porous anodic oxidation films 613 to 620 are used as masks, andthe gate insulating film 612 is etched. Then the porous anodic oxidationfilms 613 to 620 are removed, and the state of FIG. 13C is obtained.Note that reference numerals 629 to 632 shown in FIG. 13C denote thegate insulating films after processing.

Please refer to FIG. 14A. A doping process is performed with an impurityelement that imparts conductivity. Phosphorous (P) or arsenic (As) maybe used as the impurity element for a n-channel type TFT, and boron (B)or gallium (Ga) may be used for a p-channel type TFT. The impuritydoping processes for forming the n-channel type TFT and the p-channeltype TFT are divided into two stages in Embodiment 7, and then carriedout.

Impurity doping to form the n-channel type TFT is initially performed.The first impurity doping (phosphorous is used in Embodiment 7) isperformed at a high acceleration voltage of approximately 80 keV,forming an n⁻ region. The n⁻ region is regulated to have a P ionconcentration from 1×10¹⁸ to 1×10¹⁹ ions/cm².

The second impurity doping process is then performed at a lowacceleration voltage of approximately 10 keV, forming an n+region. Atthis point the acceleration voltage is low, so the gate insulating filmfunctions as a mask. Further, the doping process is regulated so thatthe n+ region has a sheet resistance of 500 Ω or less (300 Ω or lessdesirable).

Thus, through the above processes, source region 633, drain region 634,low concentration impurity regions (LDD regions) 637, and channelforming region 640 are formed for the n-channel type TFT whichconstitutes the CMOS circuit. In addition, source region 635, drainregion 636, low concentration impurity regions (LDD regions) 638 and639, and channel forming regions 641 and 642 are determined for then-channel type TFT which constitutes the pixel TFT. (See FIG. 14A.)

Note that in the state shown in FIG. 14A, the active layer of thep-channel type TFT, which constitutes the CMOS circuit, and the activelayer of the n-channel type TFT have the same composition.

Next, as shown in FIG. 14B, a resist masks 643 are formed, covering then-channel type TFTs, and a doping process is performed with an impurityion that imparts p-type conductivity (boron is used in Embodiment 7).

This process is also divided into two steps, the same as the aboveimpurity doping process. However, it is necessary to invert then-channel type conductivity to p-channel type, so B (boron) ion is dopedto a concentration several times the P ion doping concentration.

Thus, source region 644, drain region 645, low concentration impurityregions (LDD regions) 646, and channel forming region 647 are formed forthe p-channel type TFT which constitutes the CMOS circuit. (See FIG.14B.) The gate electrodes are formed using an aluminum film containing 2wt % of scandium in Embodiment 7, but the gate electrodes may also beformed using a polycrystalline silicon film. In this case the LDDregions are formed using sidewalls of SiO₂, SiN, etc.

Activation of the impurity ions is next performed with a combination offurnace annealing, laser annealing, and lamp annealing. At the sametime, any damage received by the active layers during the doping processis restored.

Please refer to FIG. 14C. Next, a laminate film from a silicon oxidefilm and a silicon nitride film is formed as a first interlayerinsulating film 648. After forming contact holes, source electrodes 649to 651, and drain electrodes 652 and 653 are formed, obtaining the stateshown in FIG. 14C. Note that an organic resin film can be used as thefirst interlayer insulating film 648.

After obtaining the state shown in FIG. 14C, a second interlayerinsulating film 654 is formed from an organic resin film to a thicknessof between 0.5 and 3 μm. (See FIG. 15A.) Polyimide, acrylic, polyimideamide, etc., can be used as the organic resin film. The following can begiven as the advantages of an organic resin film: simple filmdeposition; easily thickened film thickness; ability to reduce parasiticcapacitance because the relative dielectric constant is low; andsuperior evenness. Note that organic resin films other than those listedabove can be used.

A portion of the second interlayer insulating film 654 is removed next,and a black matrix 655 is formed from a film having light shieldingcharacteristics. In Embodiment 7 titanium is used for the black matrix655, and a storage capacitor 658 is formed between the pixel TFT drainelectrode 653 and the black matrix 655. A resin film, etc., with a blackcolored pigment can also be used as the black matrix 655.

Next, a third interlayer insulating film 656 is formed from an organicresin film to a thickness of between 0.5 and 3 μm. Polyimide, acrylic,polyimide amide, etc., can be used as the organic resin film. Note thatorganic resin films other than those listed above can be used.

A contact hole is then formed in the second interlayer insulating film654 and in the third interlayer insulating film 656, and a transparentpixel electrode 657 is formed to a thickness of 120 nm. Note thatEmbodiment 7 is an example of a transmission type active matrix typeliquid crystal display device, so a transparent conductive film such asITO is used as the conductive film that comprises the transparent pixelelectrode 657.

The entire substrate is next heated in a hydrogen atmosphere at 350° C.for between 1 and 2 hours. By performing hydrogenation of all elements,dangling bonds (unpaired bonds) throughout the films (especiallythroughout the active layers) are compensated for. Thus a CMOS circuitand a pixel region can be manufactured on the same substrate by theabove processes.

The manufacture of an active matrix type liquid crystal display devicebased on the active matrix substrate manufactured by the above processesis explained next.

An orientation film 659 is formed on the active matrix substrate in thestate of FIG. 15B. In Embodiment 7 polyimide is used for the orientationfilm 659. Next, an opposing substrate is prepared. The opposingsubstrate is formed by a glass substrate 660, an opposing electrode 661,and an orientation film 662.

Note that a polyimide film is used for the orientation film 662 inEmbodiment 7, and that a rubbing process is performed after theorientation films are formed. Also note that a polyimide with arelatively small pre-tilt angle is used in Embodiment 7.

The active matrix substrate, formed by the above processes, and theopposing substrate are joined together using a sealant material, spacer,etc., (not shown) by a known cell construction process. Afterward, aliquid crystal 663 is injected between the substrates, and thencompletely sealed with an end-sealing material (not shown in thefigures). A nematic liquid crystal is used as the liquid crystal 663 inEmbodiment 7.

Thus the transmission type active matrix type liquid crystal displaydevice as shown in FIG. 15C is completed.

[Embodiment 8]

A manufacturing process, differing from Embodiment 7, for the activematrix type liquid crystal display device of the above Embodiments 1 to6 is explained in Embodiment 8.

Please refer to FIGS. 25A to 25E. First a 200 nm thick silicon oxidefilm 5002 is formed on a glass substrate 5001 as a base film. The basefilm may also be a silicon nitride film, or a laminate of a siliconoxide film and a silicon nitride film.

Next a 30 nm thick amorphous silicon film (non-crystalline silicon film)is formed on the silicon oxide film 5002 by plasma CVD. Afterdehydrogenation processing, excimer laser annealing is performed,forming a polysilicon film (crystalline silicon film or polycrystallinesilicon film).

A known laser crystallization technique or thermal crystallizationtechnique may be used for the crystallization process. In Embodiment 8 apulse oscillation type KrF excimer laser is processed into a linearshape and crystallization of the amorphous silicon film is performed.

Note that although a polysilicon film is obtained by crystallizing theinitial film, an amorphous silicon film, by laser annealing inEmbodiment 8, but a microcrystalline silicon film may be used as theinitial film, or a polysilicon film may be directly deposited. Ofcourse, laser annealing may also be performed on a directly depositedpolysilicon film. Further, furnace annealing may be substituted forlaser annealing.

The crystalline silicon film thus formed is then patterned, formingactive layers 5003 and 5004 from island shaped silicon layers.

A gate insulating film 5005 is formed next from a silicon oxide film,covering the active layers 5003 and 5004, and gate wirings (includinggate electrodes) 5006 and 5007 having a laminate structure of tantalumand tantalum nitride are formed on top. (See FIG. 25A.)

The gate insulating film 5005 film has a thickness of 100 nm. Of course,in addition to a silicon oxide film, a silicon oxynitride film and alaminate structure of a silicon oxide film and a silicon nitride filmmay be used. Further, other metals can be used for the gate wirings 5006and 5007. However, considering later processing, it is desirable to usea material with a high etching selective ratio with respect to silicon.

After thus obtaining the state of FIG. 25A, a first phosphorous dopingprocess is performed. Doping is performed here through the gateinsulating film 5005, so the acceleration voltage is set high to 80 KeV.In addition, the dose is regulated so that the length (width) of firstimpurity regions 5008 and 5009 formed here is 0.5 μm, with a phosphorousconcentration of 1×10¹⁷ atoms/cm³. The phosphorous concentration at thispoint is denoted as n−. Note that arsenic may be used as a substitutefor phosphorous.

In addition, the first impurity regions 5008 and 5009 are formed in aself aligning manner using the gate wirings 5006 and 5007 as masks. Anintrinsic crystalline silicon layer remains under the gate wirings 5006and 5007 at this point, forming channel forming regions 5010 and 5011.However, in practice there is also a portion of the dopant that roundsto reach under the gate wirings 5006 and 5007, so the gate wirings 5006and 5007, and the first impurity regions 5008 and 5009 have an overlapstructure. (See FIG. 25 B.)

Next an amorphous silicon layer with a thickness of between 0.1 and 1 μm(typically 0.2 to 0.3 μm) is formed, covering the gate wirings 5006 and5007, and sidewalls 5012 and 5013 are formed by anisotropic etching. Thewidth of the sidewalls 5012 and 5013 (the thickness as seen from theinside wall of the gate wiring) is 0.2 μm. (See FIG. 25C.) Note that anamorphous silicon layer with no doped impurities is used in Embodiment8, so sidewalls of an intrinsic silicon layer are formed.

After obtaining the state of FIG. 25C, a second phosphorous dopingprocess is performed. The acceleration voltage is set to 80 KeV in thiscase as well, the same as for the first doping process. Further, thedose is regulated so that a phosphorous concentration of 1×10¹⁸atoms/cm³ is included in second impurity regions 5014 and 5015 formedhere. The phosphorous concentration at this point is denoted as n.

Note that the first impurity regions 5008 and 5009 remain only under thesidewalls 5012 and 5013 with the doping process shown in FIG. 25D. Thefirst impurity regions 5008 and 5009 function as 1st LDD regions.

Phosphorous is also doped into the sidewalls 5012 and 5013 in theprocess of FIG. 25D. Actually, the acceleration voltage is high, sophosphorous is distributed such that the tail of the concentrationprofile extends to the inside of the sidewalls. The resistive componentof the sidewalls can be regulated by this phosphorous. However, if thereis extreme dispersion in the phosphorous concentration distribution, thegate voltage applied to the second impurity region 5014 cannot bestopped from fluctuating for each of the elements, so precise control isnecessary at the time of doping.

Next, resist masks 5016, covering a portion of the NTFT, and 5017,covering the entire PTFT, are formed. Then the gate insulating film 5005is dry etched in this state, forming a processed gate insulating film5018. (See FIG. 25E.) At this point the length of the portion of thegate insulating film 5018 which projects beyond the sidewall 5012 (thelength of the portion of the gate insulating film 5018 which contactsthe second impurity region 5014) determines the length (width) of thesecond impurity region 5014. Therefore, it is necessary to perform maskalignment of the resist mask 5016 with good precision.

A third phosphorous doping process is performed after obtaining thestate of FIG. 25E. The acceleration voltage is set low to 10 KeV becausethis time the exposed active layer is to be doped with phosphorous. Notethat the dose is regulated so that a phosphorous concentration of 5×10²⁰atoms/cm³ is included in a third impurity region 5019 formed here. Thephosphorous concentration at this point is denoted by n+. (See FIG.26A.) Phosphorous is not doped into the areas shielded by the resistmasks 5016 and 5017, so the second impurity regions 5014 and 5015 remainas is in those areas. The second impurity region 5014 is thereforedefined, and at the same time the third impurity region 5019 is defined.

The second impurity region 5014 functions as a 2nd LDD region, and thethird impurity region 5019 functions as a source region or a drainregion.

The resist masks 5016 and 5017 are removed next, and a resist mask 5021is newly formed, covering the entire NTFT. Then the sidewall 5013 of thePTFT is first removed, and the gate insulating film 5005 is dry etched,forming a gate insulating film 5022 with the same shape as the gatewiring 5007. (See FIG. 26B.) A boron doping process is performed afterobtaining the state of FIG. 26B. The acceleration voltage is set to 10KeV, and the dose is regulated so that a boron concentration of 3×10²⁰atoms/cm³ is included in a fourth impurity region 5023 formed here. Theboron concentration at this point is denoted by p++. (See FIG. 26C.)

Boron is doped rounding to reach under the gate wiring 5007 at thistime, so the channel forming region 5011 is formed on the inside of thegate wiring 5007. Further, the first impurity region 5009 and the secondimpurity region 5015 formed on the PTFT side are inverted to p-type byboron in this process. Therefore, in practice the resistance value ofthe portions that are originally the first impurity regions and thesecond impurity regions change, but this does not become a problem bydoping boron at a sufficiently high concentration.

Thus the fourth impurity region 5023 is defined. The fourth impurityregion 5023 is formed completely in a self-aligning manner using thegate wiring 5007 as a mask, and functions as a source region or a drainregion. An LDD region and an offset region are not formed for the PTFTin Embodiment 8, but this will not become a problem because PTFTs havehigh reliability from the beginning. On the contrary, not forming an LDDregion, etc., can provide gains in the on current, so there are caseswhere this is advantageous.

Thus a channel forming region, first impurity regions, second impurityregions, and third impurity regions in the NTFT active layer, and achannel forming region and a fourth impurity region in the PTFT activelayer, are finally formed as shown in FIG. 26C.

A first interlayer insulating film 5024 is formed to a thickness of 1 μmafter obtaining the state of FIG. 26C. A silicon oxide film, a siliconnitride film, a silicon oxynitride film, an organic resin film, or alaminate of any of these films can be used as the first interlayerinsulating film 5024. An acrylic resin film is employed in Embodiment 8.

Source wiring 5025 and 5026, and a drain wiring 5027 are formed from ametallic material after forming the first interlayer insulating film5024. A three layer wiring structure of a titanium-containing aluminumfilm, sandwiched between titanium, is used in Embodiment 8.

In addition, by using a BCB (benzocyclobutene) resin film as the firstinterlayer insulating film, the evenness is high, and at the same timeit is possible to use copper as the wiring material. Copper has a lowwiring resistance, so it is extremely effective as a wiring material.

A silicon nitride film 5028 with a thickness of 50 nm is formed as apassivation film after the source wirings and drain wiring are formed. Asecond interlayer insulating film 5029 is further formed on top as aprotecting film. It is possible to use the same materials for the secondinterlayer insulating film 5029 as those that can be used for the firstinterlayer insulating film 5024. A laminate structure of a 50 nm thicksilicon oxide film and an acrylic resin film formed thereon is employedin Embodiment 8.

A CMOS circuit with a structure as shown in FIG. 26D is thus completedthrough the above processes. The NTFT has superior reliability in theCMOS circuit formed in accordance with Embodiment 8, so the reliabilityof the entire circuit is greatly raised. Furthermore, the NTFT and PTFTcharacteristic balance (the balance of electrical characteristics) issuperior with a structure in accordance with Embodiment 8.

Note that a pixel TFT can be similarly comprised of the NTFT.

A contact hole is opened to form a pixel electrode connected to thepixel TFT drain electrode after obtaining the state of FIG. 26D. Then athird interlayer film is formed, and an orientation film is formed. Inaddition, a black matrix may be formed if necessary.

Next, an opposing substrate is prepared. The opposing substrate isstructured by a glass substrate, an opposing electrode from atransparent conductive film, and an orientation film.

Note that a polyimide film is used for the orientation film inEmbodiment 8, and that a rubbing process is performed after forming theorientation film. Note also that a polyimide which possesses arelatively large pre-tilt angle is used for the orientation film inEmbodiment 8.

Next, a known cell construction process is used to join together theactive matrix substrate formed by the above processes and the opposingsubstrate, by using a sealant material, spacers, etc. Afterward, aliquid crystal is injected into the space between the two substrates,which is then completely sealed by an end-sealing material. A nematicliquid crystal is used in Embodiment 8.

Thus the transmission type active matrix type liquid crystal displaydevice is completed.

[Embodiment 9]

An example in which the crystalline semiconductor film, which serves asthe active layer in Embodiments 7 and 8, is formed by a thermalcrystallization method using a catalytic element, is shown in Embodiment9. It is desirable to use the techniques described in Japanese PatentApplication Laid-open No. Hei 7-130652 and Japanese Patent ApplicationLaid-open No. Hei 8-78329, by the applicant of the present invention,when using a catalytic element.

An example of the case where the technique described in Japanese PatentApplication Laid-open No. Hei 8-78329 is applied to the presentinvention is shown in FIGS. 27A and 27B. First, a silicon oxide film6002 is formed on a silicon substrate 6001 by thermal oxidation, and anamorphous silicon film 6003 is formed on top of that. Further, a nickelacetate salt solution, containing 10 ppm nickel by weight, is applied,forming a nickel containing layer 6004. (See FIG. 27A.)

After a dehydrogenation process at 500° C. for one hour, a heattreatment is next performed at 500 to 650° C. for between 4 and 12 hours(at 550° C. for 8 hours in Embodiment 9), forming a polysilicon film6005. The polysilicon film 6005 thus obtained has superiorcrystallinity. (See FIG. 27B.)

Afterward the polysilicon film 6005 is patterned into an active layer,and a TFT is manufactured through the same processes as those inEmbodiments 7 and 8.

Note that in addition to nickel (Ni), in the above two techniqueselements such as germanium (Ge), iron (Fe), palladium (Pd), tin (Sn),lead (Pb), cobalt (Co), platinum (Pt), copper (Cu), and gold (Au) may beused.

[Embodiment 10]

Another example of a manufacturing method for the active matrix typeliquid crystal display device of Embodiment 8 is explained in Embodiment10.

Please refer to FIGS. 28A to 28E, and to FIGS. 29A and 29B. First, anon-alkaline glass substrate, typically a Coming 1737 glass substrate,is used as a substrate 7001. Then a base film 7002 comprising siliconoxide with a thickness of 200 nm is formed on the surface of thesubstrate 7001 on which a TFT will be formed. The base film 7002 mayalso be a laminate of silicon oxide films, or may be a single siliconoxide film.

Next, a 50 nm thick amorphous silicon film is formed by plasma CVD onthe base film 7002. Dehydrogenation is desirably performed by heating atbetween 400 and 500° C., although this depends on the hydrogen contentin the amorphous silicon film. The hydrogen content in the amorphoussilicon film is reduced to 5 atm % or lower, and a crystallizationprocess is performed to form a crystalline silicon film.

A known laser crystallization technique or thermal crystallizationtechnique may be used for this crystallization process. In Embodiment10, pulse oscillation type KrF excimer laser beams are gathered into alinear shape and irradiated on the amorphous silicon film, forming thecrystalline silicon film. Note that the initial film used in Embodiment10 is an amorphous silicon film, which is crystallized by laserannealing to obtain a polysilicon film, but a microcrystalline siliconfilm or a directly deposited polysilicon film may also be used. Thedeposited polysilicon film may of course be subjected to laserannealing. Further, furnace annealing may be substituted for laserannealing. In addition, the method explained above in Embodiment 9 maybe used.

The crystalline silicon film thus formed is then patterned, formingisland shaped semiconductor layers 7003, 7004, and 7005. Next, a gateinsulating film 7006 containing silicon oxide or silicon oxide as itsmajor constituent is formed, covering the semiconductor layers7003,7004, and 7005. A 100 nm thick silicon oxynitride film is formed byplasma CVD here. Then, although not explained in FIGS. 28A to 28E, a 10to 200 nm thick (for example, 50 nm) tantalum (Ta) film is formed as afirst conductive layer, and additionally a 100 to 1000 nm thick (forexample, 200 nm) aluminum (Al) film is formed as a second conductivelayer, both by sputtering. The first conductive layer and the secondconductive layer constitute first gate electrodes on the surface of thegate insulating film 7006. Then first conductive films 7007 to 7010 andsecond conductive films 7012 to 7015, which constitute the first gateelectrodes, are formed by using a known patterning technique.

When using aluminum for the second conductive layers which constitutethe first gate electrodes, pure aluminum may be used, and aluminumalloys with an element, chosen from titanium, silicon, and scandium,doped at between 0.1 and 5 atm % may also be used. In addition, althoughnot shown in the figure, when using copper it is desirable to form asilicon nitride film on the surface of the gate insulating film 7006.

Further, FIGS. 28A to 28E shows the structure in which a supplementalcapacitor region is formed on the drain side of the n-channel TFT, whichconstitutes the pixel region. At this time wiring electrodes 7011 and7016 on the supplemental capacitor region are formed from the samematerial as that of the first gate electrodes.

After thus forming the structure shown in FIG. 28A, a first n-typeimpurity doping process is performed. Phosphorous (P), arsenic (As),antimony (Sb), etc., are known as impurity elements that impart n-typeto a crystalline semiconductor material, and phosphorous is used here inan ion doping process which uses phosphine (PH₃). The accelerationvoltage is set as high as 80 KeV for this process in order to dopephosphorous through the gate insulating film 7006, into thesemiconductor layer thereunder. Further, the impurity region thus formedwill, as will be shown later, form first impurity regions 7034, 7042,and 7046 on the n-channel type TFT, and functions as an LDD region.Therefore it is desirable that the phosphorous concentration in thisregion be in the range of 1×10¹⁶ to 1×10⁹ atoms/cm³, and it is 1×10¹⁸atoms/cm³ here.

It is necessary to activate the impurity element doped throughout thesemiconductor layer by laser annealing or heat treatment. This processmay be performed after the impurity doping process that forms the sourceregion and the drain region, but it is effective to activate by laserannealing at this stage.

The first conductive layers 7007 to 7010, the second conductive layers7012 to 7015, which constitute the first gate electrode, and wiringelectrodes 7011 and 7016 function as masks against the phosphorousdoping process. As a result, no or little phosphorous is doped into theregion directly under the first gate electrode of the semiconductorlayer, which exists through the gate insulating film. Low concentrationimpurity regions 7017 to 7023, into which phosphorous has been doped,are then formed as shown in FIG. 28B.

Next, the regions where the n-channel type TFT is formed are coveredwith resist masks 7024 and 7025, and a doping process is performed toimpart p-type conductivity on only the region where the p-channel typeTFT is formed, by using the photoresist films as masks. Boron (B),aluminum (Al), and Gallium (Ga) are known as such p-type impartingimpurity elements, and boron is doped as the impurity element here byusing diborane (B₂H₆) in an ion doping process. The acceleration voltageis again set to 80 KeV here as boron is doped to a concentration of2×10²⁰ atoms/cm³. High concentration boron doped regions 7026 and 7027are thus formed as shown in FIG. 28C. These regions will later becomethe p-channel type TFT source and drain regions.

After then removing the resist masks 7024 and 7025, a process isperformed to form the second gate electrodes. Tantalum (Ta) is used asthe second gate electrode material here, and is formed to a thickness ofbetween 100 and 1000 nm, for example, 200 nm. Patterning is thenperformed using a known technique, forming second gate electrodes 7028to 7031. The second gate electrodes are patterned at this time to have athickness of 5 μm. As a result, the second gate electrodes are formedwith a region that contacts the gate insulating film at each length of1.5 μm at both sides of the first gate electrodes.

In addition, the supplemental capacitor region is formed on the drainside of the n-channel type TFT, which constitutes the pixel region, butthe supplemental capacitor electrode 7032 is formed at the same time asthe second gate electrodes.

A second n-type imparting impurity element doping process is thenperformed, using the second gate electrodes 7028 to 7031 and thesupplemental capacitor electrode 7032 as masks. An ion doping processusing phosphine (PH₃) is also performed here. Phosphorous must passthrough the gate insulating film 7006 to be doped into the semiconductorlayers underneath, so the acceleration voltage is also set as high as 80KeV. The regions where phosphorous is doped here function as sourceregions 7035 and 7043, and drain regions 7036 and 7047, on the n-channeltype TFT, so it is desirable to have a phosphorous concentration from1×10¹⁹ to 1×10²¹ atoms/cm³. The concentration is 1×10²⁰ atoms/cm³ here.

In addition, although not shown in the figures, phosphorous may be dopeddirectly by removing the gate insulating film which covers the sourceregions 7035 and 7043, and the drain regions 7036 and 7047, thusexposing the semiconductor layers in these regions. The accelerationvoltage for ion doping can be reduced to 10 KeV if this process isadded, and phosphorous can be doped with good efficiency.

Further, phosphorous is doped to the same concentration also in a sourceregion 7039 and a drain region 7040 on the p-channel type TFT. However,boron has been doped by the previous process to twice the concentrationof phosphorous, so the conductivity type is not inverted, and there areno problems related to the operation of the p-channel type TFT.

It is necessary to perform an activation process because the impurityelements doped at various concentrations to impart n-type or p-typeconductivity are not active or effective in this state. Thermalannealing using an electric furnace, laser annealing using the abovestated excimer laser, and rapid thermal annealing (RTA) using a halogenlamp can be used for this process.

In thermal annealing, activation is made by heating at 550° C. for 2hours in a nitrogen environment. Aluminum is used for the secondconductive layers which constitute the first gate electrodes inEmbodiment 10. However, since the first conductive films and the secondgate electrodes, formed from tantalum, are formed covering the aluminum,the tantalum functions as a blocking layer, and therefore aluminum canbe prevented from diffusing into other regions. In laser annealing,activation is made by irradiation of pulse oscillation type KrF excimerlaser beams which are gathered into a linear shape. Further, an evenbetter result can be obtained by performing thermal annealing afterlaser annealing. Also, this process also has annealing effect, improvingthe crystallinity in regions of which crystallinity has been damaged byion doping.

The gate electrodes, which have the second gate electrodes covering thefirst gate electrodes, are thus formed by the above processes, and thesource region and the drain region are formed on both sides of thesecond gate electrode of the n-channel type TFT. Further, the structureis formed in a self-aligning manner in which the first impurity region,which is formed in the semiconductor layer through the gate insulatingfilm, and the region where the second gate electrode contacts the gateinsulating film, overlap with each other. The p-channel type TFT, on theother hand, has the source region and a portion of the drain regionwhich are formed to overlap the second gate electrode, but this does notbecome a problem during actual use.

A first interlayer insulating film 7049 is next formed to a thickness of1000 nm after obtaining the state of FIG. 28D. A silicon oxide film, asilicon nitride film, a silicon oxynitride film, an organic resin film,or a laminate of any of these films can be used as the first interlayerinsulating film 7049. Although not shown in the figures, a two layerstructure is used in Embodiment 10, in which a 50 nm silicon nitridefilm is formed first, followed by a 950 nm thick silicon oxide film.

The first interlayer insulating film 7049 is next patterned to formcontact holes in each of the source regions and drain regions on theTFT. Then source electrodes 7050, 7052, and 7053, and drain electrodes7051 and 7054 are formed. Although not shown in the figures, inEmbodiment 10 these electrodes are formed by patterning a three layerlaminate structure of a 100 nm titanium film, a 300 nm titaniumcontaining aluminum film, and a 150 nm titanium film, formed insuccession by sputtering.

The CMOS circuit and the pixel region are formed on the substrate 7001,as shown in FIG. 28E. In addition, the supplemental capacitor region isformed at the same time on the drain side of the pixel region n-channeltype TFT. Thus the active matrix substrate is manufactured as above.

The manufacturing process of an active matrix type liquid crystaldisplay device is next explained using FIGS. 29A and 29B, based on theCMOS circuit and the pixel region formed on the same substrate by theabove processes. First, the source electrodes 7050, 7052, and 7053, thedrain electrodes 7051 and 7054, and a passivation film 7055, whichcovers the first interlayer insulating film 7045, are formed onsubstrate in the state of FIG. 28E. The passivation film 7055 is formedfrom a 50 nm thick silicon nitride film. In addition, a secondinterlayer insulating film 7056 is formed from an organic resin to abouta 1000 nm thickness. Polyimide, acrylic, polyimide amide, etc., can beused as the organic resin film. The advantages of using an organic resinfilm include a simple method of deposition, a lower parasitic capacityowing to a low dielectric constant, and superior evenness. Note thatorganic resins other than those given above can be used. A thermalpolymerization type polyimide is used here, so it is baked at 300° C.after being applied to the substrate.

Next, a light shielding layer 7057 is formed on a portion of the secondinterlayer insulating film 7056. The shielding layer 7057 may be formedfrom a metallic film or an organic resin film containing pigments. Atitanium film is formed by sputtering here.

A third interlayer insulating film 7058 is formed after forming theshielding film 7057. It is desirable to form the third interlayerinsulating film 7058 by using an organic resin, similar to the secondinterlayer insulating film 7056. Then a contact hole that reaches thedrain electrode 7054 is formed through the second interlayer insulatingfilm 7056 and the third interlayer insulating film 7058 to form a pixelelectrode 7059. A transparent conductive film may be used for the pixelelectrode 7059 in a transmission type liquid crystal display device,while a metallic film may be used for the case of a reflection typeliquid crystal display device. A transmission type liquid crystaldisplay device is used here, so an indium-tin oxide film (ITO film) isformed by sputtering to a thickness of 100 nm, forming the pixelelectrode 7059.

An orientation film 7060 is formed after obtaining the state of FIG.29A. A polyimide resin is often used for the orientation film of anormal liquid crystal display element. An opposing electrode 7072 and anorientation film 7073 are formed on an opposing substrate 7071. Afterforming the orientation film, a rubbing process is performed to create aparallel orientation in which the liquid crystal molecules hold a fixedpre-tilt angle.

After passing through the above processes, the substrate, on which thepixel region and CMOS circuit have been formed, and the opposingsubstrate are joined together with a known cell construction processusing a sealant material, spacers (both not shown in the figures), etc.Afterward a liquid crystal material (nematic liquid crystal) 7074 isinjected into the space between the substrates, which are thencompletely sealed by an end-sealing material (not shown). Thus theactive matrix type liquid crystal display device of FIG. 29B iscompleted.

[Embodiment 11]

A nematic liquid crystal is used in Embodiments 1 to 10, but aferroelectric liquid crystal may also be used. There are no limitationson the liquid crystal material in Embodiment 11. Further, the drivingcircuit of the present invention can be used in a semiconductor displaydevice which employs any type of liquid crystal material of which theoptical parameters change in accordance with the voltage.

[Embodiment 12]

A top gate type thin film transistor is explained in Embodiments 7 and8, but a bottom gate type transistor may also be used in the presentinvention.

[Embodiment 13]

Si is used in the active layer of the TFT in Embodiments 7 and 8, but asemiconductor film containing Ge or Si_(x)Ge_(1-x) may be used in thethin film transistor which is used in the semiconductor display deviceof the present invention.

[Embodiment 14]

Embodiment 14 is an example of the present invention applied to a sourcesignal line side driving circuit of a digital drive type active matrixtype liquid crystal display device. FIG. 30 is a block diagram of anexample of the digital drive type source signal line side drivingcircuit of Embodiment 14.

A first level shifter circuit, a third level shifter circuit, a shiftregister circuit, a first latch circuit (latch circuit 1), a secondlatch circuit (latch circuit 2), a second level shifter circuit, and aD/A converter circuit are formed in the order shown in FIG. 30 for thedigital drive type source signal line side driving circuit of Embodiment14.

An example of a detailed circuit diagram of the digital drive typesource signal line side driving circuit of FIG. 30 is shown in FIG. 31.The example here is an active matrix type liquid crystal display devicefor the case of a 4 bit digital drive system.

A first level shifter circuit 3100, a shift register circuit 3101,digital decoder address lines 3102 a to 3102 d, first latch circuits(LAT1) 3103, second latch circuits (LAT2) 3104, a latch pulse line 3105,D/A converter circuits 3106, gradation voltage lines 3107, source signallines 3108, a second level shifter circuit 3109, and a third levelshifter circuit 3110 are arranged as shown in FIG. 31. Note that fourlatch circuits are grouped together and shown as the latch circuits 3103and 3104 (LAT1 and LAT2) for convenience. In addition, for convenience'ssake, a level shifter circuit that increases the voltage amplitude levelof a clock signal, and a level shifter circuit that increases thevoltage amplitude level of a start pulse signal are grouped together andshown as the first level shifter circuit 3100.

A clock signal CLK is input to the first level shifter circuit 3100 fromexternal to the source signal line side driving circuit. The voltageamplitude level of the clock signal is as low as possible within therange in which the first level shifter circuit 3100 can operate becauseof the demand to suppress unwanted radiation to a level at which it doesnot become a problem. In addition, this is necessary in order tosuppress power consumption.

The clock signal input to the first level shifter circuit 3100 is madehigher in voltage and then output. It is necessary that the voltageamplitude level of the clock signal at this time be increased to avoltage amplitude level at which the shift register circuit 3101 TFT isnot damaged by punch through or hot electrons due to the short channeleffect, and at which the TFT, with a manufacturable channel length, canoperate.

The clock signal, with its voltage amplitude level increased by thefirst level shifter circuit 3100, is input to the shift register circuit3101. In addition, the start pulse signal, with its voltage amplitudelevel increased by the first level shifter circuit 3100, is input toshifter register circuit 3101 through the line shown in FIG. 31. Theshift register circuit 3101 starts operation based on the clock signalinput to the shift register circuit 3101, and in accordance with thestart pulse signal (SP) also input to the shift register circuit 3101,and creates a timing signal that determines the timing for writing adigital signal to the first latch circuit 3103.

The digital signal (digital gradation signal) is input to the thirdlevel shifter circuit 3110 through the digital decoder address lines3102 a to 3102 d. The input digital signal is made higher in voltage andthen output. It is necessary to increase the voltage amplitude level ofthe digital signal at this time to a voltage amplitude level at whichthe shift register circuit 3101 TFT is not damaged by punch through orhot electrons due to the short channel effect, and at which the TFT,with a manufacturable channel length, can operate. The digital signalthat has been made higher in voltage and then output is written in orderto the first latch circuit 3103 in accordance with the timing signalcreated by the shift register circuit 3101. The most significant bit(MSB) of the digital signal is input from the digital decoder addressline 3102 a, and the least significant bit (LSB) of the digital signalis input from the digital decoder address line 3102 b.

After the writing of the digital signal is completed with respect to thefirst latch circuit 3103, the digital signal written into the firstlatch circuit 3103 is transmitted and written to the second latchcircuit 3104, simultaneous with a latch pulse which flows in the latchpulse line 3105 in time with the operation timing of the shift registercircuit 3101.

The writing of another digital signal to the first latch circuit 3101,which is again supplied by the digital decoder, is performed in orderand in accordance with a signal from the shift register circuit 3101,after the transmission of the previous digital signal to the secondlatch circuit 3104 is complete.

During the second one-line period, the digital signal with a voltageamplitude level corresponding to the digital signal transmitted to thesecond latch circuit 3104, in time with the start of the second one-lineperiod, is input to the second level shifter circuit 3104.

The digital signal input to the second level shifter circuit 3109 ismade higher in voltage. It is necessary for the digital signal to beincreased at this time to a voltage amplitude level that includes acertain fixed margin voltage.

The margin voltage is in order to convert the digital signal input tothe D/A converter circuit 3106 to an analog signal. The size of themargin voltage is dependent upon the voltage of the largest analogsignal output from the D/A converter circuit 3106.

The digital signal with voltage increased by the second level shiftercircuit 3109 is input to the D/A converter circuit 3106 and converted toan analog signal, and the analog signal is supplied to the source signallines 3108 corresponding to a one-line period interval. Switching ofcorresponding pixel TFTs is performed in accordance with a selectionsignal from the shift register circuit in a gate signal line sidedriving circuit, and the liquid crystal molecules are driven.

By repeatedly performing the above operations for the number of scanninglines, one screen (one frame) is formed. In general, the writing of 60frames of images per second is performed in an active matrix type liquidcrystal display device.

As such, by forming level shifter circuits before and after a shiftregister circuit in a digital drive type source signal line side drivingcircuit with the present invention, a clock signal which has a voltageamplitude level low enough so that the shift register circuit TFT is notdamaged by punch through or hot electrons due to the short channeleffect, and high enough so that a TFT with a manufacturable channellength will operate, can be input to the shift register circuit. As aresult, the shift register circuit can be operated at higher speed.

In addition, even if the voltage amplitude level of the clock signalinput from external to the source signal line side driving circuit isreduced as much as possible within the range in which the level shiftercircuit can operate, high-speed operation of the shift register circuitis possible, so power consumption and unwanted radiation can besuppressed to such an extent that they do not become problems.

Further, the frequency of a digital signal is several tens of MHz largerthan the frequency of an image signal of an analog type driving circuit,so unwanted radiation becomes a problem. Therefore it is desirable toreduce the voltage of the digital signal, but if the voltage amplitudelevel of the digital signal is lower than the gradation voltage, itbecomes difficult to convert the digital signal into an analog signal bythe D/A converter. With the present invention, it is possible to reducethe voltage amplitude level of a digital signal, input to a latchcircuit from external to a digital drive type source signal line sidedriving circuit, as much as possible within the range at which a levelshifter circuit can operate. Therefore, the voltage of the digitalsignal input to the latch circuit can be suppressed, and it is possibleto suppress unwanted radiation and power consumption.

An example of the present invention applied to a digital circuit sourcesignal line side driving circuit is explained in Embodiment 14, but thepresent invention is not limited to the preferred embodiment ofEmbodiment 14. It is also possible to use the present invention in adigital circuit gate signal line side driving circuit, and additionallyin both a digital circuit source signal line side driving circuit and adigital circuit gate signal line side driving circuit.

[Embodiment 15]

In addition to nematic liquid crystals, it is possible to use many kindsof liquid crystals for the liquid crystal display devices of the presentinvention. For example, it is possible to use the liquid crystalsdisclosed in: Furue, H. et al., “Characteristics and Driving Scheme ofPolymer-Stabilized Monostable FLCD Exhibiting Fast Response Time andHigh Contrast Ratio with Gray-Scale Capability”, SID, 1998; Yoshida, T.et al., “A Full-Color Thresholdless Antiferroelectric LCD ExhibitingWide Viewing Angle with Fast Response Time”, SID Digest, 841, 1997;Inui, S. et al., “Thresholdless Antiferroelectricity in Liquid Crystalsand its Application to Displays”, J. Mater. Chem., 6(4), p. 671-3, 1996;and in U.S. Pat. No. 5,594,569.

The resulting electro-optical characteristics of a monostable FLC areshown in FIG. 33. In the drawings, a ferroelectric liquid crystal (FLC)exhibiting a phase transition system of an isotropic phase—cholestericphase—phase is used to perform a phase transition between thecholesteric phase and the chiralsmectic phase, while applying a DCvoltage, and the cone edge is made to nearly conform with the rubbingdirection. The display mode of a ferroelectric liquid crystal like thatshown in FIG. 33 is called “half-V switching mode.” The vertical axis ofthe graph shown in FIG. 33 is the transmittance (in arbitrary units),and the horizontal axis is the applied voltage. Details regarding the“half-V switching mode” may be found in: Terada, et al., “Half-VSwitching Mode FLCD”, Proceedings of the 46th Applied PhysicsAssociation Lectures, p. 1316, March 1999; and in Yoshihara, et al.,“Time Partition Full Color LCD with Ferroelectric Liquid Crystal”,Liquid Crystals, vol. 3, no. 3, p. 190.

As shown in FIG. 33, it is apparent that if this type of ferroelectricmixed liquid crystal is used, it is possible to have a low voltage driveand a gradation display. A ferroelectric liquid crystal that shows theseelectro-optical characteristics can be used for the liquid crystaldisplay device of the present invention.

In addition, a liquid crystal that exhibits an anti-ferroelectric phasein a certain temperature range is called an anti-ferroelectric liquidcrystal (AFLC). Among mixed liquid crystals, which have ananti-ferroelectric liquid crystal, there is one so-called thresholdlessantiferroelectric mixed liquid crystal that shows electro-opticalresponse characteristics in which the transmittance continuously changesin response to the electric field. Some thresholdless antiferroelectricmixed liquid crystals show V-type electro-optical responsecharacteristics, and also have been found one that has a drive voltageof approximately +2.5 V (when the cell thickness is between 1 and 2 μm).

Further, in general the spontaneous polarization of a thresholdlessantiferroelectric mixed liquid crystal is large, and the dielectricconstant of the liquid crystal itself is high. Thus, a relatively largestorage capacitor is required for pixels when a thresholdlessantiferroelectric mixed liquid crystal is used for a liquid crystaldisplay device. Therefore it is desirable to use a thresholdlessantiferroelectric mixed liquid crystal that has a smaller spontaneouspolarization.

Note that by using this type of thresholdless antiferroelectric mixedliquid crystal for the liquid crystal display devices of the presentinvention, a low drive voltage can be realized, so low power consumptioncan also be realized.

[Embodiment 16]

This example demonstrates a process for producing an active matrix typeEL (electroluminescence) display device according to the invention ofthe present application.

FIG. 34A is a top view showing an EL display device, which was producedaccording to the invention of the present application. In FIG. 34A,there are shown a substrate 4010, a pixel region 4011, a source signalline side driving circuit 4012, and a gate signal line side drivingcircuit 4013, each driving circuit connecting to wirings 4014-4016 whichreach FPC 4017 leading to external equipment.

The pixel region, preferably together with the driving circuit, isenclosed by a covering material 6000, a sealing material (or housingmaterial) 7000, and an end-sealing material (or second sealing material)7001.

FIG. 34B is a sectional view showing the structure of the EL displaydevice in this Example. There is shown a substrate 4010, a base film4021, a TFT 4022 (CMOS circuit consisting of an n-channel type TFT and ap-channel type TFT) for the driving circuit, and a TFT 4023 for thepixel region to control current to the EL element. These TFTs may beformed using conventional structure such as bottom gate or top gatestructure.

Incidentally, the present invention is used in the source signal linedriving circuit 4012 or the gate signal line driving circuit 4013.

Upon completion of TFT 4022 (for the driving circuit) and TFT 4023 (forthe pixel region) according to the invention of the present application,a pixel electrode 4027 is formed on the interlayer insulating film(planarizing film) 4026 made of a resin. This pixel electrode 4027 iselectrically connected to the drain of TFT 4023 for the pixel region.When the pixel electrode comprises a transparent conductive film, ap-channel type TFT is used as the TFT for the pixel region. Thetransparent conductive film may be formed from a compound (called ITO)of indium oxide and tin oxide or a compound of indium oxide and zincoxide. On the pixel electrode 4027 is formed an insulating film 4028, inwhich is formed an opening above the pixel electrode 4027.

Subsequently, the EL layer 4029 is formed. It may be of single-layerstructure or multi-layer structure by freely combining known ELmaterials such as a hole injection layer, a hole transport layer, alight emitting layer, an electron transport layer, and an electroninjection layer. Any known technology may be available for suchstructure. The EL material is either a low-molecular material or ahigh-molecular material (polymer). The former may be applied by vapordeposition, and the latter may be applied by a simple method such asspin coating, printing, or ink-jet method.

In this example, the EL layer is formed by vapor deposition through ashadow mask. The resulting EL layer permits each pixel to emit lightdiffering in wavelength (red, green, and blue). This realizes the colordisplay. Alternative systems available include the combination of colorconversion layer (CCM) and color filter and the combination of whitelight emitting layer and color filter. Needless to say, the EL displaydevice may be monochromatic.

A cathode 4030 is formed on the EL layer 4029. Prior to this step, it isdesirable to clear moisture and oxygen as much as possible from theinterface between the EL layer 4029 and the cathode 4030. This objectmay be achieved by forming the EL layer 4029 and the cathode 4030subsequently in a vacuum, or by forming the EL layer 4029 in an inertatmosphere and then forming the cathode 4030 in the same atmospherewithout exposing to air. In this Example, the desired film was formed byusing a film-forming apparatus of multi-chamber system (cluster toolsystem).

The multi-layer structure composed of lithium fluoride film and aluminumfilm is used in this Example as the cathode 4030. To be concrete, the ELlayer 4029 is coated by vapor deposition with a lithium fluoride film (1nm thick) and an aluminum film (300 nm thick) sequentially. Needless tosay, the cathode 4030 may be formed from MgAg electrode which is a knowncathode material. Subsequently, the cathode 4030 is connected to awiring 4016 in the region indicated by 4031. The wiring 4016 to supply aprescribed voltage to the cathode 4030 is connected to the FPC 4017through an electrically conductive paste material 4032.

The electrical connection between the cathode 4030 and the wiring 4016in the region 4031 needs contact holes in the interlayer insulating film4026 and the insulating film 4028. These contact holes may be formedwhen the interlayer insulating film 4026 undergoes etching to form thecontact hole for the pixel electrode or when the insulating film 4028undergoes etching to form the opening before the EL layer is formed.When the insulating film 4028 undergoes etching, the interlayerinsulating film 4026 may be etched simultaneously. Contact holes of goodshape may be formed if the interlayer insulating film 4026 and theinsulating film 4028 are made of the same material.

Then, a passivation film 6003, a filling material 6004 and a coveringmaterial 6000 are formed so that these layers cover the EL element.

Furthermore, the sealing material 7000 is formed inside of the coveringmaterial 6000 and the substrate 4010 such as surrounding the EL element,and the end-sealing material 7001 is formed outside of the sealingmaterial 7000.

The filling material 6004 is formed to cover the EL element and alsofunctions as an adhesive to adhere to the covering material 6000. As thefilling material 6004, PVC (polyvinyl chloride), an epoxy resin, asilicon resin, PVB (polyvinyl butyral), or EVA (ethylenvinyl acetate)can be utilized. It is preferable to form a desiccant in the fillingmaterial 6004, since a moisture absorption can be maintained.

Also, spacers can be contained in the filling material 6004. It ispreferable to use spherical spacers comprising barium oxide to maintainthe moisture absorption in the spacers.

In the case of that the spaces are contained in the filling material,the passivation film 6003 can relieve the pressure of the spacers. Ofcourse, the other film different from the passivation film, such as anorganic resin, can be used for relieving the pressure of the spacers.

As the covering material 6000, a glass plate, an aluminum plate, astainless plate, a FRP (Fiberglass-Reinforced Plastics) plate, a PVF(polyvinyl fluoride) film, a Mylar film, a polyester film or an acrylfilm can be used. In a case that PVB or EVA is employed as the fillingmaterial 6004, it is preferable to use an aluminum foil with a thicknessof some tens of μm sandwiched by a PVF film or a Mylar film.

It is noted that the covering material 6000 should have a lighttransparency with accordance to a light emitting direction (a lightradiation direction) from the EL element.

The wiring 4016 is electrically connected to FPC 4017 through the gapbetween the sealing material 7000 and the end-sealing material 7001, andthe substrate 4010. As in the wiring 4016 explained above, other wirings4014 and 4015 are also electrically connected to FPC 4017 under thesealing material 4018.

In this embodiment, the covering material 6000 is adhered afterdisposing the filling material 6004, and the sealing material 7000 isattached so as to cover the side face( an exposed face) of the fillingmaterial. However, the filling material 6004 can be disposed afterattaching the cover material 6000 and the sealing material 7000. In thiscase, an opening is formed for injecting the filling material into aspace between the substrate 4010, the covering material 6000 and thesealing material 7000. Then the space is evacuated (less than 10⁻² Torr)and the opening is immersed in the filling material tank. And thefilling material fills the space by making the outside pressure of thespace higher than the inside pressure of the space.

[Embodiment 17]

In this embodiment, another active matrix type EL display device havinga different structure from the embodiment 16 is explained, as shown inFIGS. 35A and 35B. The same reference numerals in FIGS. 35A and 35B asin FIGS. 34A and 34B indicate same constitutive elements, so anexplanation is omitted.

FIG. 35A shows a top view of the EL module in this embodiment and FIG.35B shows a sectional view of A-A′ of FIG. 35A.

According to Embodiment 16, the passivation film 6003 is formed to covera surface of the EL element.

The filling material 6004 is formed to cover the EL element and alsofunctions as an adhesive to adhere to the covering material 6000. As thefilling material 6004, PVC (polyvinyl chloride), an epoxy resin, asilicon resin, PVB (polyvinyl butyral), or EVA (ethylenvinyl acetate)can be utilized. It is preferable to form a desiccant in the fillingmaterial 6004, since a moisture absorption can be maintained.

Also, spacers can be contained in the filling material 6004. It ispreferable to use spherical spacers comprising barium oxide to maintainthe moisture absorption in the spacers.

In the case of that the spaces are contained in the filling material,the passivation film 6003 can relieve the pressure of the spacers. Ofcourse, the other film different from the passivation film, such as anorganic resin, can be used for relieving the pressure of the spacers.

As the covering material 6000, a glass plate, an aluminum plate, astainless plate, a FRP (Fiberglass-Reinforced Plastics) plate, a PVF(polyvinyl fluoride) film, a Mylar film, a polyester film or an acrylfilm can be used. In a case that PVB or EVA is employed as the fillingmaterial 6004, it is preferable to use an aluminum foil with a thicknessof some tens of um sandwiched by a PVF film or a Mylar film.

It is noted that the covering material 6000 should have a lighttransparency with accordance to a light emitting direction (a lightradiation direction) from the EL element.

Next, the covering material 6000 is adhered using the filling material6004. Then, the flame material 6001 is attached to cover side portions(exposed faces) of the filling material 6004. The flame material 6001 isadhered by the sealing material (acts as an adhesive) 6002. As thesealing material 6002, a light curable resin is preferable. Also, athermal curable resin can be employed if a heat resistance of the ELlayer is admitted. It is preferable for the sealing material 6002 not topass moisture and oxygen. In addition, it is possible to add a desiccantinside the sealing material 6002.

The wiring 4016 is electrically connected to FPC 4017 through the gapbetween the sealing material 6002 and the substrate 4010. As in thewiring 4016 explained above, other wirings 4014 and 4015 are alsoelectrically connected to FPC 4017 under the sealing material 6002.

In this embodiment, the covering material 6000 is adhered afterdisposing the filling material 6004, and the sealing material 7000 isattached so as to cover the side face( an exposed face) of the fillingmaterial. However, the filling material 6004 can be disposed afterattaching the cover material 6000 and the sealing material 7000. In thiscase, an opening is formed for injecting the filling material into aspace between the substrate 4010, the covering material 6000 and thesealing material 7000. Then the space is evacuated (less than 10⁻² Torr)and the opening is immersed in the filling material tank. And thefilling material fills the space by making the outside pressure of thespace higher than the inside pressure of the space.

[Embodiment 18]

This example can be applied to the EL display panel having a structureas shown in Embodiment 16 and 17. FIG. 36 shows the cross section of thepixel region; FIG. 37A shows the top view thereof; and FIG. 37B showsthe circuit structure for the pixel region. In FIG. 36, FIG. 37A andFIG. 37B, the same reference numerals are referred to for the sameportions, as being common thereto.

In FIG. 36, the switching TFT 3502 formed on the substrate 3501 is aconventional NTFT. In this Embodiment, it has a double-gate structure,but its structure and fabrication process do not so much differ from thestructures and the fabrication processes illustrated hereinabove, andtheir description is omitted herein. However, the double-gate structureof the switching TFT 3502 has substantially two TFTs as connected inseries, and therefore has the advantage of reducing the off-current topass therethrough. In this Embodiment, the switching TFT 3502 has such adouble-gate structure, but is not limitative. It may have a single-gatestructure or a triple-gate structure, or even any other multi-gatestructure having more than three gates. As the case may be, theswitching TFT 3502 may be PTFT of the invention.

The current-control TFT 3503 is a conventional NTFT. The drain wire 35in the switching TFT 3502 is electrically connected with the gateelectrode 37 of the current-control TFT, via the wire 36 therebetween.The wire indicated by 38 is a gate wire for electrically connecting thegate electrodes 39 a and 39 b in the switching TFT 3502.

The current-control TFT is a unit for controlling the quantity ofcurrent that passes through the EL device. Therefore, a large quantityof current passes through it, and the unit, current-control TFT has ahigh risk of thermal degradation and degradation with hot carriers. Tothis unit, therefore, the structure of the invention is extremelyfavorable, in which an LDD region is so constructed that the gateelectrode overlaps with the drain area in the current-control TFT, via agate insulating film therebetween.

In this Embodiment, the current-control TFT 3503 is illustrated to havea single-gate structure, but it may have a multi-gate structure withplural TFTs connected in series. In addition, plural TFTs may beconnected in parallel so that the channel forming region issubstantially divided into plural sections. In the structure of thattype, heat radiation can be effected efficiently. The structure isadvantageous for protecting the device with it from thermaldeterioration.

As in FIG. 37A, the wire to be the gate electrode 37 in thecurrent-control TFT 3503 overlaps with the drain wire 40 therein in theregion indicated by 3504, via an insulating film therebetween. In thisstate, the region indicated by 3504 forms a capacitor. The capacitor3504 functions to retain the voltage applied to the gate electrode inthe current-control TFT 3503. The drain wire 40 is connected with thecurrent supply line (power line) 3506, from which a constant voltage isall the time applied to the drain wire 40.

On the switching TFT 3502 and the current-control TFT 3503, a firstpassivation film 41 is formed. On the film 41, formed is a planarizingfilm 42 of an insulating resin. It is extremely important that thedifference in level of the layered portions in TFT is removed throughplanarization with the planarizing film 42. This is because the EL layerto be formed on the previously formed layers in the later step isextremely thin, and if there exist a difference in level of thepreviously formed layers, the EL device will be often troubled by lightemission failure. Accordingly, it is desirable to previously planarizeas much as possible the previously formed layers before the formation ofthe pixel electrode thereon so that the EL layer could be formed on theplanarized surface.

The reference numeral 43 indicates a pixel electrode (a cathode in theEL device) of an conductive film with high reflectivity. The pixelelectrode 43 is electrically connected with the drain region in thecurrent-control TFT 3503. It is preferable that the pixel electrode 43is of a low-resistance conductive film of an aluminum alloy, a copperalloy or a silver alloy, or of a laminate of those films.Needless-to-say, the pixel electrode 43 may have a laminate structurewith any other conductive films.

In the recess (this corresponds to the pixel) formed between the banks44 a and 44 b of an insulating film (preferably of a resin), thelight-emitting layer 45 is formed. In the illustrated structure, onlyone pixel is shown, but plural light-emitting layers could be separatelyformed in different pixels, corresponding to different colors of R(red), G (green) and B (blue). The organic EL material for thelight-emitting layer may be any -conjugated polymer material. Typicalpolymer materials usable herein include polyparaphenylenevinylene (PVV)materials, polyvinylcarbazole (PVK) materials, polyfluorene materials,etc.

Various types of PVV-type organic EL materials are known, such as thosedisclosed in H. Shenk, H. Becker, O. Gelsen, E. Klunge, W. Kreuder, andH. Spreitzer; Polymers for Light Emitting Diodes, Euro DisplayProceedings, 1999, pp. 33-37 and in Japanese Patent Laid-Open No.10-92576 (1998). Any of such known materials are usable herein.

Concretely, cyanopolyphenylenevinylenes may be used for red-emittinglayers; polyphenylenevinylenes may be for green-emitting layers; andpolyphenylenevinylenes or polyalkylphenylenes may be for blue-emittinglayers. The thickness of the film for the light-emitting layers may fallbetween 30 and 150 nm (preferably between 40 and 100 nm).

These compounds mentioned above are referred to merely for examples oforganic EL materials employable herein and are not limitative at all.The light-emitting layer may be combined with a charge transportationlayer or a charge injection layer in any desired manner to form theintended EL layer (this is for light emission and for carrier transferfor light emission).

Specifically, this embodiments to demonstrate an embodiment of usingpolymer materials to form light-emitting layers, which, however, is notlimitative. Low-molecular organic EL materials may also be used forlight-emitting layers. For charge transportation layers and chargeinjection layers, further employable are inorganic materials such assilicon carbide, etc. Various organic EL materials and inorganicmaterials for those layers are known, any of which are usable herein.

In this Embodiment, a hole injection layer 46 of PEDOT (polythiophene)or PAni (polyaniline) is formed on the light-emitting layer 45 to give alaminate structure for the EL layer. On the hole injection layer 46,formed is an anode 47 of a transparent conductive film. In thisEmbodiment, the light having been emitted by the light-emitting layer 45radiates therefrom in the direction toward the top surface (that is, inthe upward direction of TFT). Therefore, in this, the anode musttransmit light. For the transparent conductive film for the anode,usable are compounds of indium oxide and tin oxide, and compounds ofindium oxide and zinc oxide. However, since the anode is formed afterthe light-emitting layer and the hole injection layer having poor heatresistance have been formed, it is preferable that the transparentconductive film for the anode is of a material capable of being formedinto a film at as low as possible temperatures.

When the anode 47 is formed, the EL device 3505 is finished. The ELdevice 3505 thus fabricated herein indicates a capacitor comprising thepixel electrode (cathode) 43, the light-emitting layer 45, the holeinjection layer 46 and the anode 47. As in FIG. 37A, the region of thepixel electrode 43 is nearly the same as the area of the pixel.Therefore, in this, the entire pixel functions as the EL device.Accordingly, the light utility efficiency of the EL device fabricatedherein is high, and the device can display bright images.

In this Embodiment, a second passivation film 48 is formed on the anode47. For the second passivation film 48, preferably used is a siliconnitride film or a silicon nitride oxide film. The object of the film 48is to insulate the EL device from the outward environment. The film 48has the function of preventing the organic EL material from beingdegraded through oxidation and has the function of preventing it fromdegassing. With the second passivation film 48 of that type, thereliability of the EL display device is improved.

As described hereinabove, the EL display panel of the inventionfabricated in this Embodiment has a pixel region for the pixel havingthe constitution as in FIG. 36, and has the switching TFT through whichthe off-current to pass is very small to a satisfactory degree, and thecurrent-control TFT resistant to hot carrier injection. Accordingly, theEL display panel fabricated herein has high reliability and can displaygood images.

The constitution of this Embodiment can be combined with anyconstitution of Embodiments 1 to 17 in any desired manner.

[Embodiment 19]

This Embodiment is to demonstrate a modification of the EL display panelof Embodiment 18, in which the EL device 3505 in the pixel region has areversed structure. For this Embodiment, referred to is FIG. 38. Theconstitution of the EL display panel of this Embodiment differs fromthat illustrated in FIG. 36 only in the EL device portion and thecurrent-control TFT portion. Therefore, the description of the otherportions except those different portions is omitted herein.

In FIG. 38, the current-control TFT 3701 may be a conventional PT Inthis Embodiment, the pixel electrode (anode) 50 is of a transparentconductive film. Concretely, used is an conductive film of a compound ofindium oxide and zinc oxide. Needless-to-say, also usable is anconductive film of a compound of indium oxide and tin oxide.

After the banks 51 a and 51 b of an insulating film have been formed, alight-emitting layer 52 of polyvinylcarbazole is formed between them ina solution coating method. On the light-emitting layer 52, formed are anelectron injection layer 53 of acetylacetonatopotassium, and a cathode54 of an aluminum alloy. In this case, the cathode 54 serves also as apassivation film. Thus is fabricated the EL device 3701.

In this Embodiment, the light having been emitted by the light-emittinglayer radiates in the direction toward the substrate with TFT formedthereon, as in the direction of the arrow illustrated.

The constitution of this Embodiment can be combined with anyconstitution of Embodiments 1 to 17 in any desired manner.

[Embodiment 20]

This Embodiment is to demonstrate modifications of the pixel with thecircuit structure of FIG. 37B. The modifications are as in FIG. 39A toFIG. 39C. In this Embodiment illustrated in those FIG. 38A to FIG. 38C,3801 indicates the source signal line for the switching TFT 3802; 3803indicates the gate signal line for the switching TFT 3802; 3804indicates a current-control TFT; 3805 indicates a capacitor; 3806 and3808 indicate current supply lines; and 3807 indicates an EL element.

In the embodiment of FIG. 39A, the current supply line 3806 is common tothe two pixels. Specifically, this embodiment is characterized in thattwo pixels are lineal-symmetrically formed with the current supply line3806 being the center between them. Since the number of current supplylines can be reduced therein, this embodiment is advantageous in thatthe pixel region can be much finer and thinner.

In the embodiment of FIG. 39B, the current supply line 3808 is formed inparallel to the gate wire 3803. Specifically, in this, the currentsupply line 3808 is so constructed that it does not overlap with thegate wire 3803, but is not limitative. Being different from theillustrated case, the two may overlap with each other via an insulatingfilm therebetween so far as they are of different layers. Since thecurrent supply line 3808 and the gate wire 3803 may enjoy the commonexclusive area therein, this embodiment is advantageous in that thepixel pattern can be much finer and thinner.

The structure of the embodiment of FIG. 39C is characterized in that thecurrent supply line 3808 is formed in parallel to the gate wires 3803,like in FIG. 39B, and that two pixels are lineal-symmetrically formedwith the current supply line 3808 being the center between them. Inthis, it is also effective to provide the current supply line 3808 insuch a manner that it overlaps with any one of the gate wires 3803.Since the number of current supply lines can be reduced therein, thisembodiment is advantageous in that the pixel pattern can be much finerand thinner.

The constitution of this Embodiment can be combined with anyconstitution of Embodiment 1 to 17 in any desired manner.

[Embodiment 21]

The embodiment of Embodiment 18 illustrated in FIG. 37A and FIG. 37B isprovided with the capacitor 3504 which acts to retain the voltageapplied to the gate in the current-control TFT 3503. In the embodiment,however, the capacitor 3504 may be omitted.

In the embodiment of Embodiment 18, the current-control TFT 3503 isNTFT, and the LDD region is so formed that it overlaps with the gateelectrode via the gate insulating film therebetween. In the overlappedregion, formed is a parasitic capacitance generally referred to as agate capacitance. The embodiment of this Embodiment is characterized inthat the parasitic capacitance is positively utilized in place of thecapacitor 3504.

The parasitic capacitance in question varies, depending on the area inwhich the gate electrode overlaps with the LDD region, and is thereforedetermined according to the length of the LDD region in the overlappedarea.

Also in the embodiments of Embodiment 20 illustrated in FIG. 39A, FIG.39B and FIG. 39C, the capacitor 3805 can be omitted.

The constitution of this Embodiment can be combined with anyconstitution of Embodiment 1 to 20 in any desired manner.

[Embodiment 22]

There are various uses for electronic equipment that uses asemiconductor display device (typically an active matrix liquid crystaldisplay device, an active matrix type EL display device, or an activematrix type EC display device) manufactured in accordance with thepresent invention. Electronic equipment into which a semiconductordisplay device that uses a driving circuit manufactured in accordancewith the present invention is incorporated.

The following can be given as examples of this type of electronicequipment: video cameras; still cameras; digital cameras; projectors(rear type and front type); head mount displays (goggle type displays);game machines; car navigation systems; personal computers; portableinformation terminals (such as mobile computers, portable telephones,and electronic books), etc. Some examples of these are shown in FIGS.16A-16E, 17A-17B, and 32A to 32C.

FIG. 16A is a portable telephone, and is composed of a main body 1101, asound output section 1102, a sound input section 1103, a semiconductordisplay device 1104, operation switches 1105, and an antenna 1106. Thepresent invention can be applied to the semiconductor display device1104, to the sound input section 1103, and to other signal controlcircuits.

FIG. 16B is a video camera, and is composed of a main body 1107, asemiconductor display device 1108, a sound input section 1109, operationswitches 1110, a battery 1111, and an image receiving section 1112. Thepresent invention can be applied to the semiconductor display device1108, to the sound input section 1109, and to other signal controlcircuits.

FIG. 16C is a mobile computer, and is composed of a main body 1113, acamera section 1114, an image receiving section 1115, operating switches1116, and a semiconductor display device 1117. The present invention canbe applied to the semiconductor display device 1117 and to other signalcontrol circuits.

FIG. 16D is a head mount display, and is composed of a main body 1118,semiconductor display devices 1119, mirrors 1120, and back lights 1121.The present invention can be applied to the semiconductor display device1119 and to other signal control circuits.

FIG. 16E is a head mount display device, and is composed of asemiconductor display device 1123, and a band section 1124. The headmount display device shown in FIG. 16E is equipped with only onesemiconductor display device. The present invention can be applied tothe semiconductor display device 1123 and to other signal controlcircuits.

FIG. 17A is a rear type projector, and is composed of a main body 1201,a semiconductor display device 1202, a light source 1203, an opticalsystem 1204, and a screen 1205. Note that it is desirable to be cable ofchanging the screen angle of a rear type projector, with the main bodyfixed, depending upon the location of the viewer. Note also that byusing three semiconductor display devices 1202 (corresponding to R, G,and B light, respectively) a rear type projector with higher resolutionand higher definition can be realized.

FIG. 17B is a front type projector, and is composed of a main body 1206,a semiconductor display device 1207, a light source 1208, a reflector1209, and a screen 1210. Note that by using three semiconductor displaydevices 1207 (corresponding to R, G, and B light, respectively) a fronttype projector with higher resolution and higher definition can berealized.

FIG. 32A is a personal computer, and is composed of a main body 7501, animage input section 7502, a display device 7503, and a keyboard 7504.The present invention can be applied to the image input section 7502, tothe semiconductor display device 7503, and to other signal controlcircuits.

FIG. 32B is a goggle type display, and is composed of a main body 7301,a semiconductor display device 7302, and an arm section 7303. Thepresent invention can be applied to the semiconductor display device7302, and to other signal control circuits.

FIG. 32C is a player which uses a recording medium on which a program isrecorded (hereafter referred to as a recording medium), and is composedof a main body 7401, a semiconductor display device 7402, a speakersection 7403, a recording medium 7404, and operation switches 7405. Notethat music appreciation, film appreciation, games, and the use of theInternet can be performed with this device used by a DVD (digitalversatile disk), a CD, etc., as a recording medium. The. presentinvention can be applied to the semiconductor display device 7402, andto other signal control circuits.

As shown above, the present invention's applicable range is extremelywide, and it can be applied to electronic equipment in all fields.Further, the semiconductor display device of Embodiment 22 can berealized with a composition that uses a combination with any ofEmbodiments 1 to 21.

With the present invention, by arranging level shifter circuits bothbefore and after the shift register circuit, the clock signal of such avoltage amplitude level that the shift register circuit TFT is notdamaged due to punch through or hot electrons caused by the shortchannel effect, and that a TFT with a manufacturable channel lengthoperates allows the shift register circuit to operate. As a result,high-speed operation can be performed without damage to the shiftregister circuit, and it is possible to drive the liquid crystals in asaturation state. In addition, even if the voltage amplitude level ofthe clock signal input from external to the source signal line sidedriving circuit is reduced as much as possible within the range in whichthe level shifter circuit can operate, high-speed operation of the shiftregister circuit is possible, so power consumption and unwantedradiation can be suppressed to such an extent that they do not becomeproblems.

What is claimed is:
 1. A method for driving a semiconductor devicecomprising: inputting a signal to a first level shifter circuit in asource signal line side driving circuit; increasing a voltage of thesignal, by the first level shifter circuit, to a first voltage amplitudelevel at which it is sufficient for a shift register circuit to operate;inputting the increased signal to the shift register circuit; creating atiming signal, by the shift register circuit, based on the signal inputfrom the first level shifter circuit; inputting the timing signal to asecond level shifter circuit; increasing a voltage amplitude level ofthe timing signal by the second level shifter circuit; inputting theincreased timing signal to a sampling circuit; and sampling an imagesignal, by the sampling circuit, in accordance with the increased timingsignal; and supplying the sampled signal to source signal linesconnected to the source signal line side driving circuit.
 2. A methodaccording to claim 1, wherein the source signal line side drivingcircuit is formed on the same substrate as a pixel region.
 3. A methodaccording to claim 1, wherein the semiconductor device is a liquidcrystal display device.
 4. A method according to claim 1, wherein thesemiconductor device is an electroluminescence display device.
 5. Amethod according to claim 1, wherein the semiconductor device is used inan electronic equipment selected from the group consisting of a videocamera, a still camera, a digital camera, a rear type projector, a fronttype projector, a head mount display, a goggle type display, a gamemachine, a car navigation system, a personal computer, a portableinformation terminal, a mobile computer, a portable telephone, and anelectronic book.
 6. A method for driving a semiconductor devicecomprising: inputting a clock signal having a first voltage amplitudelevel to a first level shifter circuit in a source signal line sidedriving circuit; increasing the first voltage amplitude level of theclock signal to a second voltage amplitude level by the first levelshifter circuit; inputting the clock signal having the second voltageamplitude level to a shift register circuit, wherein shift registercircuit operates based on the input clock signal, and in accordance witha start pulse signal input to the shift register circuit at the sametime, and a timing signal for sampling an image is created in order, thetiming signal having a third voltage amplitude level; input the timingsignal to a second level shifter circuit; increasing the third voltageamplitude level of the timing signal to a fourth voltage amplitudelevel; inputting the timing signal having the fourth voltage amplitudelevel to a sampling circuit, wherein the sampling circuit operates basedon the timing signal with a voltage amplitude level increased by thesecond level shifter circuit, and an image signal is sampled; andsupplying the sampled image signal to source signal lines.
 7. A methodaccording to claim 6, wherein the source signal line side drivingcircuit is formed on the same substrate as a pixel region.
 8. A methodaccording to claim 6, wherein the semiconductor device is a liquidcrystal display device.
 9. A method according to claim 6, wherein thesemiconductor device is an electroluminescence display device.
 10. Amethod according to claim 6, wherein the semiconductor device is used inan electronic equipment selected from the group consisting of a videocamera, a still camera, a digital camera, a rear type projector, a fronttype projector, a head mount display, a goggle type display, a gamemachine, a car navigation system, a personal computer, a portableinformation terminal, a mobile computer, a portable telephone, and anelectronic book.
 11. A method for driving a semiconductor devicecomprising: inputting a signal to a gate signal line side drivingcircuit, increasing a voltage of the signal by a first level shiftercircuit in the gate signal line side driving circuit, to a first voltageamplitude level at which it is sufficient for a shift register circuitto operate; inputting the increased signal to the shift register circuitfrom the first level shifter circuit; creating a selection signal, bythe shift register circuit, based on the increased input signal;inputting the selection signal to a second level shifter circuit;increasing a second voltage amplitude level of the input selectionsignal by the second level shifter circuit, to a third voltage amplitudelevel at which it is sufficient for all pixel thin film transistorsconnected to gate signal lines to reliably operate; and supplyingincreased selection signal to the gate signal lines.
 12. A methodaccording to claim 11, wherein the gate signal line side driving circuitis formed on the same substrate as a pixel region.
 13. A methodaccording to claim 11, wherein the increased selection signal isinputted to the gate signal lines through a buffer circuit.
 14. A methodaccording to claim 11, wherein the semiconductor device is a liquidcrystal display device.
 15. A method according to claim 11, wherein thesemiconductor device is an electroluminescence display device.
 16. Amethod according to claim 11, wherein the semiconductor device is usedin an electronic equipment selected from the group consisting of a videocamera, a still camera, a digital camera, a rear type projector, a fronttype projector, a head mount display, a goggle type display, a gamemachine, a car navigation system, a personal computer, a portableinformation terminal, a mobile computer, a portable telephone, and anelectronic book.
 17. A method for driving a semiconductor devicecomprising: inputting a clock signal to a first level shifter circuit toin a gate signal line side driving circuit, the clock signal having afirst voltage amplitude level at which it is sufficient for the firstlevel shifter circuit to operate; increasing the first voltage amplitudelevel of the clock signal, by the first level shifter circuit, to asecond voltage amplitude level at which it is sufficient for a shiftregister circuit to operate; inputting the increased clock signal to theshift register circuit; creating a selection signal, by the shiftregister circuit, based on the increased clock signal input to the shiftregister circuit; inputting the created selection signal to a secondlevel shifter circuit; increasing a third voltage amplitude level of theselection signal, by the second level shifter circuit, to a fourthvoltage amplitude level at which it is sufficient for all of pixel thinfilm transistors connected to gate signal lines to reliably operate; andsupplying the selection signal, which has been increased in voltage bythe second level shifter circuit, to the gate signal lines.
 18. A methodaccording to claim 17, the gate signal line side driving circuit isformed on the same substrate as a pixel region.
 19. A method accordingto claim 17, wherein the increased selection signal is inputted to thegate signal lines through a buffer circuit.
 20. A method according toclaim 17, wherein the semiconductor device is a liquid crystal displaydevice.
 21. A method according to claim 17, wherein the semiconductordevice is an electroluminescence display device.
 22. A method accordingto claim 17, wherein the semiconductor device is used in an electronicequipment selected from the group consisting of a video camera, a stillcamera, a digital camera, a rear type projector, a front type projector,a head mount display, a goggle type display, a game machine, a carnavigation system, a personal computer, a portable information terminal,a mobile computer, a portable telephone, and an electronic book.